java两个字符串的差异对比与显示（8/25修订）

问题：有两串字符串，现在需要把里面不同的内容标记出来。
解决：
这里用到一个java类Diff_match_patch（文章最下面显示，该文件出自网络）

主要代码

public static void main(String[] arge){            //字符串1  altbe  字符串2  altaf            List<Integer> beList = rememberSpacing(altbe);            List<Integer> afList = rememberSpacing(altaf);            altbe = altbe.replace(" ", "");            altaf = altaf.replace(" ", "");            LinkedList<Diff> t = diff_match_patch.diff_main(altbe,altaf);            StringBuffer s1 = new StringBuffer();            StringBuffer s2 = new StringBuffer();            Integer indexBe = 0;            Integer indexAf = 0;            for (Diff diff : t) {                StringBuffer diffTextBe = new StringBuffer(diff.text);                StringBuffer diffTextAf = new StringBuffer(diff.text);                if(diff.operation.toString().equalsIgnoreCase("EQUAL")){                    addSpacing(beList, indexBe, diffTextBe);                    addSpacing(afList, indexAf, diffTextAf);                    s1.append(diffTextBe);                    s2.append(diffTextAf);                    indexBe+=diffTextBe.length();                    indexAf+=diffTextAf.length();                }                indexBe = appendString2("DELETE", diff, s1, s2,beList,indexBe);                indexAf = appendString2("INSERT", diff, s2, s1,afList,indexAf);            }    System.out.println(s1.toString());    System.out.println(s2.toString());}public static void appendString(String type, Diff diff, StringBuffer sbOne,StringBuffer sbTwo){        if (type.equals(diff.operation.toString())) {            if(" ".equals(diff.text)){                sbOne.append(" ");                sbTwo.append(" ");            }else{                sbOne.append("<em class='f-required'>").append(diff.text).append("</em>");            }        }    }public static List<Integer> rememberSpacing(String str){        List<Integer> list = new ArrayList<Integer>();        for(int i = 0;i < str.length();i++){            if(' '==str.charAt(i)){                list.add(i);            }        }        return list;    }public static void addSpacing(List<Integer> list,Integer index,StringBuffer str){        for(Integer o:list){            if(o>=index&&o<index+str.length()){                str.insert(o-index, ' ');            }        }    }public static Integer appendString2(String type, Diff diff, StringBuffer sbOne,            StringBuffer sbTwo,List<Integer> list,Integer i){        Integer result = i;        if (type.equals(diff.operation.toString())) {            StringBuffer sb = new StringBuffer(diff.text);            for(Integer o:list){                if(o>=i&&o<i+sb.length()){                    sb.insert(o-i, ' ');                }            }            sbOne.append("<em class='f-required'>").append(sb).append("</em>");            result = i+sb.length();        }        return result;    }

本文上版对字符串的处理采用“+”和subString（）处理。现在改为StringBuffer后，效率显著提升。惊呆小博主了。

Diff_match_patch类

/* * Diff Match and Patch * * Copyright 2006 Google Inc. * http://code.google.com/p/google-diff-match-patch/ * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * *   http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */import java.io.UnsupportedEncodingException;import java.net.URLDecoder;import java.net.URLEncoder;import java.util.ArrayList;import java.util.Arrays;import java.util.HashMap;import java.util.HashSet;import java.util.LinkedList;import java.util.List;import java.util.ListIterator;import java.util.Map;import java.util.Set;import java.util.Stack;import java.util.regex.Matcher;import java.util.regex.Pattern;/* * Functions for diff, match and patch. * Computes the difference between two texts to create a patch. * Applies the patch onto another text, allowing for errors. * * @author [e-mail] (Neil Fraser) *//** * Class containing the diff, match and patch methods. * Also contains the behaviour settings. */public class Diff_match_patch {  // Defaults.  // Set these on your diff_match_patch instance to override the defaults.  /**   * Number of seconds to map a diff before giving up (0 for infinity).   */  public float Diff_Timeout = 1.0f;  /**   * Cost of an empty edit operation in terms of edit characters.   */  public short Diff_EditCost = 4;  /**   * The size beyond which the double-ended diff activates.   * Double-ending is twice as fast, but less accurate.   */  public short Diff_DualThreshold = 32;  /**   * At what point is no match declared (0.0 = perfection, 1.0 = very loose).   */  public float Match_Threshold = 0.5f;  /**   * How far to search for a match (0 = exact location, 1000+ = broad match).   * A match this many characters away from the expected location will add   * 1.0 to the score (0.0 is a perfect match).   */  public int Match_Distance = 1000;  /**   * When deleting a large block of text (over ~64 characters), how close does   * the contents have to match the expected contents. (0.0 = perfection,   * 1.0 = very loose).  Note that Match_Threshold controls how closely the   * end points of a delete need to match.   */  public float Patch_DeleteThreshold = 0.5f;  /**   * Chunk size for context length.   */  public short Patch_Margin = 4;  /**   * The number of bits in an int.   */  private int Match_MaxBits = 32;  /**   * Internal class for returning results from diff_linesToChars().   * Other less paranoid languages just use a three-element array.   */  protected static class LinesToCharsResult {    protected String chars1;    protected String chars2;    protected List<String> lineArray;    protected LinesToCharsResult(String chars1, String chars2,        List<String> lineArray) {      this.chars1 = chars1;      this.chars2 = chars2;      this.lineArray = lineArray;    }  }  //  DIFF FUNCTIONS  /**   * The data structure representing a diff is a Linked list of Diff objects:   * {Diff(Operation.DELETE, "Hello"), Diff(Operation.INSERT, "Goodbye"),   *  Diff(Operation.EQUAL, " world.")}   * which means: delete "Hello", add "Goodbye" and keep " world."   */  public enum Operation {    DELETE, INSERT, EQUAL  }  /**   * Find the differences between two texts.   * Run a faster slightly less optimal diff   * This method allows the 'checklines' of diff_main() to be optional.   * Most of the time checklines is wanted, so default to true.   * @param text1 Old string to be diffed.   * @param text2 New string to be diffed.   * @return Linked List of Diff objects.   */  public LinkedList<Diff> diff_main(String text1, String text2) {    return diff_main(text1, text2, true);  }  /**   * Find the differences between two texts.  Simplifies the problem by   * stripping any common prefix or suffix off the texts before diffing.   * @param text1 Old string to be diffed.   * @param text2 New string to be diffed.   * @param checklines Speedup flag.  If false, then don't run a   *     line-level diff first to identify the changed areas.   *     If true, then run a faster slightly less optimal diff   * @return Linked List of Diff objects.   */  public LinkedList<Diff> diff_main(String text1, String text2, boolean checklines) {    // Check for equality (speedup)    LinkedList<Diff> diffs;    if (text1.equals(text2)) {      diffs = new LinkedList<Diff>();      diffs.add(new Diff(Operation.EQUAL, text1));      return diffs;    }    // Trim off common prefix (speedup)    int commonlength = diff_commonPrefix(text1, text2);    String commonprefix = text1.substring(0, commonlength);    text1 = text1.substring(commonlength);    text2 = text2.substring(commonlength);    // Trim off common suffix (speedup)    commonlength = diff_commonSuffix(text1, text2);    String commonsuffix = text1.substring(text1.length() - commonlength);    text1 = text1.substring(0, text1.length() - commonlength);    text2 = text2.substring(0, text2.length() - commonlength);    // Compute the diff on the middle block    diffs = diff_compute(text1, text2, checklines);    // Restore the prefix and suffix    if (commonprefix.length() != 0) {      diffs.addFirst(new Diff(Operation.EQUAL, commonprefix));    }    if (commonsuffix.length() != 0) {      diffs.addLast(new Diff(Operation.EQUAL, commonsuffix));    }    diff_cleanupMerge(diffs);    return diffs;  }  /**   * Find the differences between two texts.  Assumes that the texts do not   * have any common prefix or suffix.   * @param text1 Old string to be diffed.   * @param text2 New string to be diffed.   * @param checklines Speedup flag.  If false, then don't run a   *     line-level diff first to identify the changed areas.   *     If true, then run a faster slightly less optimal diff   * @return Linked List of Diff objects.   */  protected LinkedList<Diff> diff_compute(String text1, String text2,boolean checklines) {    LinkedList<Diff> diffs = new LinkedList<Diff>();    if (text1.length() == 0) {      // Just add some text (speedup)      diffs.add(new Diff(Operation.INSERT, text2));      return diffs;    }    if (text2.length() == 0) {      // Just delete some text (speedup)      diffs.add(new Diff(Operation.DELETE, text1));      return diffs;    }    String longtext = text1.length() > text2.length() ? text1 : text2;    String shorttext = text1.length() > text2.length() ? text2 : text1;    int i = longtext.indexOf(shorttext);    if (i != -1) {      // Shorter text is inside the longer text (speedup)      Operation op = (text1.length() > text2.length()) ?                     Operation.DELETE : Operation.INSERT;      diffs.add(new Diff(op, longtext.substring(0, i)));      diffs.add(new Diff(Operation.EQUAL, shorttext));      diffs.add(new Diff(op, longtext.substring(i + shorttext.length())));      return diffs;    }    longtext = shorttext = null;  // Garbage collect.    // Check to see if the problem can be split in two.    String[] hm = diff_halfMatch(text1, text2);    if (hm != null) {      // A half-match was found, sort out the return data.      String text1_a = hm[0];      String text1_b = hm[1];      String text2_a = hm[2];      String text2_b = hm[3];      String mid_common = hm[4];      // Send both pairs off for separate processing.      LinkedList<Diff> diffs_a = diff_main(text1_a, text2_a, checklines);      LinkedList<Diff> diffs_b = diff_main(text1_b, text2_b, checklines);      // Merge the results.      diffs = diffs_a;      diffs.add(new Diff(Operation.EQUAL, mid_common));      diffs.addAll(diffs_b);      return diffs;    }    // Perform a real diff.    if (checklines && (text1.length() < 100 || text2.length() < 100)) {      checklines = false;  // Too trivial for the overhead.    }    List<String> linearray = null;    if (checklines) {      // Scan the text on a line-by-line basis first.      LinesToCharsResult b = diff_linesToChars(text1, text2);      text1 = b.chars1;      text2 = b.chars2;      linearray = b.lineArray;    }    diffs = diff_map(text1, text2);    if (diffs == null) {      // No acceptable result.      diffs = new LinkedList<Diff>();      diffs.add(new Diff(Operation.DELETE, text1));      diffs.add(new Diff(Operation.INSERT, text2));    }    if (checklines) {      // Convert the diff back to original text.      diff_charsToLines(diffs, linearray);      // Eliminate freak matches (e.g. blank lines)      diff_cleanupSemantic(diffs);      // Rediff any replacement blocks, this time character-by-character.      // Add a dummy entry at the end.      diffs.add(new Diff(Operation.EQUAL, ""));      int count_delete = 0;      int count_insert = 0;      String text_delete = "";      String text_insert = "";      ListIterator<Diff> pointer = diffs.listIterator();      Diff thisDiff = pointer.next();      while (thisDiff != null) {        switch (thisDiff.operation) {        case INSERT:          count_insert++;          text_insert += thisDiff.text;          break;        case DELETE:          count_delete++;          text_delete += thisDiff.text;          break;        case EQUAL:          // Upon reaching an equality, check for prior redundancies.          if (count_delete >= 1 && count_insert >= 1) {            // Delete the offending records and add the merged ones.            pointer.previous();            for (int j = 0; j < count_delete + count_insert; j++) {              pointer.previous();              pointer.remove();            }            for (Diff newDiff : diff_main(text_delete, text_insert, false)) {              pointer.add(newDiff);            }          }          count_insert = 0;          count_delete = 0;          text_delete = "";          text_insert = "";          break;        }        thisDiff = pointer.hasNext() ? pointer.next() : null;      }      diffs.removeLast();  // Remove the dummy entry at the end.    }    return diffs;  }  /**   * Split two texts into a list of strings.  Reduce the texts to a string of   * hashes where each Unicode character represents one line.   * @param text1 First string.   * @param text2 Second string.   * @return An object containing the encoded text1, the encoded text2 and   *     the List of unique strings.  The zeroth element of the List of   *     unique strings is intentionally blank.   */  protected LinesToCharsResult diff_linesToChars(String text1, String text2) {    List<String> lineArray = new ArrayList<String>();    Map<String, Integer> lineHash = new HashMap<String, Integer>();    // e.g. linearray[4] == "Hello\n"    // e.g. linehash.get("Hello\n") == 4    // "\x00" is a valid character, but various debuggers don't like it.    // So we'll insert a junk entry to avoid generating a null character.    lineArray.add("");    String chars1 = diff_linesToCharsMunge(text1, lineArray, lineHash);    String chars2 = diff_linesToCharsMunge(text2, lineArray, lineHash);    return new LinesToCharsResult(chars1, chars2, lineArray);  }  /**   * Split a text into a list of strings.  Reduce the texts to a string of   * hashes where each Unicode character represents one line.   * @param text String to encode.   * @param lineArray List of unique strings.   * @param lineHash Map of strings to indices.   * @return Encoded string.   */  private String diff_linesToCharsMunge(String text, List<String> lineArray,                                        Map<String, Integer> lineHash) {    int lineStart = 0;    int lineEnd = -1;    String line;    StringBuilder chars = new StringBuilder();    // Walk the text, pulling out a substring for each line.    // text.split('\n') would would temporarily double our memory footprint.    // Modifying text would create many large strings to garbage collect.    while (lineEnd < text.length() - 1) {      lineEnd = text.indexOf('\n', lineStart);      if (lineEnd == -1) {        lineEnd = text.length() - 1;      }      line = text.substring(lineStart, lineEnd + 1);      lineStart = lineEnd + 1;      if (lineHash.containsKey(line)) {        chars.append(String.valueOf((char) (int) lineHash.get(line)));      } else {        lineArray.add(line);        lineHash.put(line, lineArray.size() - 1);        chars.append(String.valueOf((char) (lineArray.size() - 1)));      }    }    return chars.toString();  }  /**   * Rehydrate the text in a diff from a string of line hashes to real lines of   * text.   * @param diffs LinkedList of Diff objects.   * @param lineArray List of unique strings.   */  protected void diff_charsToLines(LinkedList<Diff> diffs,                                  List<String> lineArray) {    StringBuilder text;    for (Diff diff : diffs) {      text = new StringBuilder();      for (int y = 0; y < diff.text.length(); y++) {        text.append(lineArray.get(diff.text.charAt(y)));      }      diff.text = text.toString();    }  }  /**   * Explore the intersection points between the two texts.   * @param text1 Old string to be diffed.   * @param text2 New string to be diffed.   * @return LinkedList of Diff objects or null if no diff available.   */  protected LinkedList<Diff> diff_map(String text1, String text2) {    long ms_end = System.currentTimeMillis() + (long) (Diff_Timeout * 1000);    // Cache the text lengths to prevent multiple calls.    int text1_length = text1.length();    int text2_length = text2.length();    int max_d = text1_length + text2_length - 1;    boolean doubleEnd = Diff_DualThreshold * 2 < max_d;    List<Set<Long>> v_map1 = new ArrayList<Set<Long>>();    List<Set<Long>> v_map2 = new ArrayList<Set<Long>>();    Map<Integer, Integer> v1 = new HashMap<Integer, Integer>();    Map<Integer, Integer> v2 = new HashMap<Integer, Integer>();    v1.put(1, 0);    v2.put(1, 0);    int x, y;    Long footstep = 0L;  // Used to track overlapping paths.    Map<Long, Integer> footsteps = new HashMap<Long, Integer>();    boolean done = false;    // If the total number of characters is odd, then the front path will    // collide with the reverse path.    boolean front = ((text1_length + text2_length) % 2 == 1);    for (int d = 0; d < max_d; d++) {      // Bail out if timeout reached.      if (Diff_Timeout > 0 && System.currentTimeMillis() > ms_end) {        return null;      }      // Walk the front path one step.      v_map1.add(new HashSet<Long>());  // Adds at index 'd'.      for (int k = -d; k <= d; k += 2) {        if (k == -d || k != d && v1.get(k - 1) < v1.get(k + 1)) {          x = v1.get(k + 1);        } else {          x = v1.get(k - 1) + 1;        }        y = x - k;        if (doubleEnd) {          footstep = diff_footprint(x, y);          if (front && (footsteps.containsKey(footstep))) {            done = true;          }          if (!front) {            footsteps.put(footstep, d);          }        }        while (!done && x < text1_length && y < text2_length               && text1.charAt(x) == text2.charAt(y)) {          x++;          y++;          if (doubleEnd) {            footstep = diff_footprint(x, y);            if (front && (footsteps.containsKey(footstep))) {              done = true;            }            if (!front) {              footsteps.put(footstep, d);            }          }        }        v1.put(k, x);        v_map1.get(d).add(diff_footprint(x, y));        if (x == text1_length && y == text2_length) {          // Reached the end in single-path mode.          return diff_path1(v_map1, text1, text2);        } else if (done) {          // Front path ran over reverse path.          v_map2 = v_map2.subList(0, footsteps.get(footstep) + 1);          LinkedList<Diff> a = diff_path1(v_map1, text1.substring(0, x),                                          text2.substring(0, y));          a.addAll(diff_path2(v_map2, text1.substring(x), text2.substring(y)));          return a;        }      }      if (doubleEnd) {        // Walk the reverse path one step.        v_map2.add(new HashSet<Long>());  // Adds at index 'd'.        for (int k = -d; k <= d; k += 2) {          if (k == -d || k != d && v2.get(k - 1) < v2.get(k + 1)) {            x = v2.get(k + 1);          } else {            x = v2.get(k - 1) + 1;          }          y = x - k;          footstep = diff_footprint(text1_length - x, text2_length - y);          if (!front && (footsteps.containsKey(footstep))) {            done = true;          }          if (front) {            footsteps.put(footstep, d);          }          while (!done && x < text1_length && y < text2_length                 && text1.charAt(text1_length - x - 1)                 == text2.charAt(text2_length - y - 1)) {            x++;            y++;            footstep = diff_footprint(text1_length - x, text2_length - y);            if (!front && (footsteps.containsKey(footstep))) {              done = true;            }            if (front) {              footsteps.put(footstep, d);            }          }          v2.put(k, x);          v_map2.get(d).add(diff_footprint(x, y));          if (done) {            // Reverse path ran over front path.            v_map1 = v_map1.subList(0, footsteps.get(footstep) + 1);            LinkedList<Diff> a                = diff_path1(v_map1, text1.substring(0, text1_length - x),                             text2.substring(0, text2_length - y));            a.addAll(diff_path2(v_map2, text1.substring(text1_length - x),                                text2.substring(text2_length - y)));            return a;          }        }      }    }    // Number of diffs equals number of characters, no commonality at all.    return null;  }  /**   * Work from the middle back to the start to determine the path.   * @param v_map List of path sets.   * @param text1 Old string fragment to be diffed.   * @param text2 New string fragment to be diffed.   * @return LinkedList of Diff objects.   */  protected LinkedList<Diff> diff_path1(List<Set<Long>> v_map,                                        String text1, String text2) {    LinkedList<Diff> path = new LinkedList<Diff>();    int x = text1.length();    int y = text2.length();    Operation last_op = null;    for (int d = v_map.size() - 2; d >= 0; d--) {      while (true) {        if (v_map.get(d).contains(diff_footprint(x - 1, y))) {          x--;          if (last_op == Operation.DELETE) {            path.getFirst().text = text1.charAt(x) + path.getFirst().text;          } else {            path.addFirst(new Diff(Operation.DELETE,                                   text1.substring(x, x + 1)));          }          last_op = Operation.DELETE;          break;        } else if (v_map.get(d).contains(diff_footprint(x, y - 1))) {          y--;          if (last_op == Operation.INSERT) {            path.getFirst().text = text2.charAt(y) + path.getFirst().text;          } else {            path.addFirst(new Diff(Operation.INSERT,                                   text2.substring(y, y + 1)));          }          last_op = Operation.INSERT;          break;        } else {          x--;          y--;          assert (text1.charAt(x) == text2.charAt(y))                 : "No diagonal.  Can't happen. (diff_path1)";          if (last_op == Operation.EQUAL) {            path.getFirst().text = text1.charAt(x) + path.getFirst().text;          } else {            path.addFirst(new Diff(Operation.EQUAL, text1.substring(x, x + 1)));          }          last_op = Operation.EQUAL;        }      }    }    return path;  }  /**   * Work from the middle back to the end to determine the path.   * @param v_map List of path sets.   * @param text1 Old string fragment to be diffed.   * @param text2 New string fragment to be diffed.   * @return LinkedList of Diff objects.   */  protected LinkedList<Diff> diff_path2(List<Set<Long>> v_map,                                        String text1, String text2) {    LinkedList<Diff> path = new LinkedList<Diff>();    int x = text1.length();    int y = text2.length();    Operation last_op = null;    for (int d = v_map.size() - 2; d >= 0; d--) {      while (true) {        if (v_map.get(d).contains(diff_footprint(x - 1, y))) {          x--;          if (last_op == Operation.DELETE) {            path.getLast().text += text1.charAt(text1.length() - x - 1);          } else {            path.addLast(new Diff(Operation.DELETE,                text1.substring(text1.length() - x - 1, text1.length() - x)));          }          last_op = Operation.DELETE;          break;        } else if (v_map.get(d).contains(diff_footprint(x, y - 1))) {          y--;          if (last_op == Operation.INSERT) {            path.getLast().text += text2.charAt(text2.length() - y - 1);          } else {            path.addLast(new Diff(Operation.INSERT,                text2.substring(text2.length() - y - 1, text2.length() - y)));          }          last_op = Operation.INSERT;          break;        } else {          x--;          y--;          assert (text1.charAt(text1.length() - x - 1)                  == text2.charAt(text2.length() - y - 1))                 : "No diagonal.  Can't happen. (diff_path2)";          if (last_op == Operation.EQUAL) {            path.getLast().text += text1.charAt(text1.length() - x - 1);          } else {            path.addLast(new Diff(Operation.EQUAL,                text1.substring(text1.length() - x - 1, text1.length() - x)));          }          last_op = Operation.EQUAL;        }      }    }    return path;  }  /**   * Compute a good hash of two integers.   * @param x First int.   * @param y Second int.   * @return A long made up of both ints.   */  protected long diff_footprint(int x, int y) {    // The maximum size for a long is 9,223,372,036,854,775,807    // The maximum size for an int is 2,147,483,647    // Two ints fit nicely in one long.    long result = x;    result = result << 32;    result += y;    return result;  }  /**   * Determine the common prefix of two strings   * @param text1 First string.   * @param text2 Second string.   * @return The number of characters common to the start of each string.   */  public int diff_commonPrefix(String text1, String text2) {    // Performance analysis: http://neil.fraser.name/news/2007/10/09/    int n = Math.min(text1.length(), text2.length());    for (int i = 0; i < n; i++) {      if (text1.charAt(i) != text2.charAt(i)) {        return i;      }    }    return n;  }  /**   * Determine the common suffix of two strings   * @param text1 First string.   * @param text2 Second string.   * @return The number of characters common to the end of each string.   */  public int diff_commonSuffix(String text1, String text2) {    // Performance analysis: http://neil.fraser.name/news/2007/10/09/    int text1_length = text1.length();    int text2_length = text2.length();    int n = Math.min(text1_length, text2_length);    for (int i = 1; i <= n; i++) {      if (text1.charAt(text1_length - i) != text2.charAt(text2_length - i)) {        return i - 1;      }    }    return n;  }  /**   * Do the two texts share a substring which is at least half the length of   * the longer text?   * @param text1 First string.   * @param text2 Second string.   * @return Five element String array, containing the prefix of text1, the   *     suffix of text1, the prefix of text2, the suffix of text2 and the   *     common middle.  Or null if there was no match.   */  protected String[] diff_halfMatch(String text1, String text2) {    String longtext = text1.length() > text2.length() ? text1 : text2;    String shorttext = text1.length() > text2.length() ? text2 : text1;    if (longtext.length() < 10 || shorttext.length() < 1) {      return null;  // Pointless.    }    // First check if the second quarter is the seed for a half-match.    String[] hm1 = diff_halfMatchI(longtext, shorttext,                                   (longtext.length() + 3) / 4);    // Check again based on the third quarter.    String[] hm2 = diff_halfMatchI(longtext, shorttext,                                   (longtext.length() + 1) / 2);    String[] hm;    if (hm1 == null && hm2 == null) {      return null;    } else if (hm2 == null) {      hm = hm1;    } else if (hm1 == null) {      hm = hm2;    } else {      // Both matched.  Select the longest.      hm = hm1[4].length() > hm2[4].length() ? hm1 : hm2;    }    // A half-match was found, sort out the return data.    if (text1.length() > text2.length()) {      return hm;      //return new String[]{hm[0], hm[1], hm[2], hm[3], hm[4]};    } else {      return new String[]{hm[2], hm[3], hm[0], hm[1], hm[4]};    }  }  /**   * Does a substring of shorttext exist within longtext such that the   * substring is at least half the length of longtext?   * @param longtext Longer string.   * @param shorttext Shorter string.   * @param i Start index of quarter length substring within longtext.   * @return Five element String array, containing the prefix of longtext, the   *     suffix of longtext, the prefix of shorttext, the suffix of shorttext   *     and the common middle.  Or null if there was no match.   */  private String[] diff_halfMatchI(String longtext, String shorttext, int i) {    // Start with a 1/4 length substring at position i as a seed.    String seed = longtext.substring(i, i + longtext.length() / 4);    int j = -1;    String best_common = "";    String best_longtext_a = "", best_longtext_b = "";    String best_shorttext_a = "", best_shorttext_b = "";    while ((j = shorttext.indexOf(seed, j + 1)) != -1) {      int prefixLength = diff_commonPrefix(longtext.substring(i),  shorttext.substring(j));      int suffixLength = diff_commonSuffix(longtext.substring(0, i),shorttext.substring(0, j));      if (best_common.length() < suffixLength + prefixLength) {        best_common = shorttext.substring(j - suffixLength, j)            + shorttext.substring(j, j + prefixLength);        best_longtext_a = longtext.substring(0, i - suffixLength);        best_longtext_b = longtext.substring(i + prefixLength);        best_shorttext_a = shorttext.substring(0, j - suffixLength);        best_shorttext_b = shorttext.substring(j + prefixLength);      }    }    if (best_common.length() >= longtext.length() / 2) {      return new String[]{best_longtext_a, best_longtext_b,                          best_shorttext_a, best_shorttext_b, best_common};    } else {      return null;    }  }  /**   * Reduce the number of edits by eliminating semantically trivial equalities.   * @param diffs LinkedList of Diff objects.   */  public void diff_cleanupSemantic(LinkedList<Diff> diffs) {    if (diffs.isEmpty()) {      return;    }    boolean changes = false;    Stack<Diff> equalities = new Stack<Diff>();  // Stack of qualities.    String lastequality = null; // Always equal to equalities.lastElement().text    ListIterator<Diff> pointer = diffs.listIterator();    // Number of characters that changed prior to the equality.    int length_changes1 = 0;    // Number of characters that changed after the equality.    int length_changes2 = 0;    Diff thisDiff = pointer.next();    while (thisDiff != null) {      if (thisDiff.operation == Operation.EQUAL) {        // equality found        equalities.push(thisDiff);        length_changes1 = length_changes2;        length_changes2 = 0;        lastequality = thisDiff.text;      } else {        // an insertion or deletion        length_changes2 += thisDiff.text.length();        if (lastequality != null && (lastequality.length() <= length_changes1)            && (lastequality.length() <= length_changes2)) {          //System.out.println("Splitting: '" + lastequality + "'");          // Walk back to offending equality.          while (thisDiff != equalities.lastElement()) {            thisDiff = pointer.previous();          }          pointer.next();          // Replace equality with a delete.          pointer.set(new Diff(Operation.DELETE, lastequality));          // Insert a corresponding an insert.          pointer.add(new Diff(Operation.INSERT, lastequality));          equalities.pop();  // Throw away the equality we just deleted.          if (!equalities.empty()) {            // Throw away the previous equality (it needs to be reevaluated).            equalities.pop();          }          if (equalities.empty()) {            // There are no previous equalities, walk back to the start.            while (pointer.hasPrevious()) {              pointer.previous();            }          } else {            // There is a safe equality we can fall back to.            thisDiff = equalities.lastElement();            while (thisDiff != pointer.previous()) {              // Intentionally empty loop.            }          }          length_changes1 = 0;  // Reset the counters.          length_changes2 = 0;          lastequality = null;          changes = true;        }      }      thisDiff = pointer.hasNext() ? pointer.next() : null;    }    if (changes) {      diff_cleanupMerge(diffs);    }    diff_cleanupSemanticLossless(diffs);  }  /**   * Look for single edits surrounded on both sides by equalities   * which can be shifted sideways to align the edit to a word boundary.   * e.g: The c<ins>at c</ins>ame. -> The <ins>cat </ins>came.   * @param diffs LinkedList of Diff objects.   */  public void diff_cleanupSemanticLossless(LinkedList<Diff> diffs) {    String equality1, edit, equality2;    String commonString;    int commonOffset;    int score, bestScore;    String bestEquality1, bestEdit, bestEquality2;    // Create a new iterator at the start.    ListIterator<Diff> pointer = diffs.listIterator();    Diff prevDiff = pointer.hasNext() ? pointer.next() : null;    Diff thisDiff = pointer.hasNext() ? pointer.next() : null;    Diff nextDiff = pointer.hasNext() ? pointer.next() : null;    // Intentionally ignore the first and last element (don't need checking).    while (nextDiff != null) {      if (prevDiff.operation == Operation.EQUAL &&          nextDiff.operation == Operation.EQUAL) {        // This is a single edit surrounded by equalities.        equality1 = prevDiff.text;        edit = thisDiff.text;        equality2 = nextDiff.text;        // First, shift the edit as far left as possible.        commonOffset = diff_commonSuffix(equality1, edit);        if (commonOffset != 0) {          commonString = edit.substring(edit.length() - commonOffset);          equality1 = equality1.substring(0, equality1.length() - commonOffset);          edit = commonString + edit.substring(0, edit.length() - commonOffset);          equality2 = commonString + equality2;        }        // Second, step character by character right, looking for the best fit.        bestEquality1 = equality1;        bestEdit = edit;        bestEquality2 = equality2;        bestScore = diff_cleanupSemanticScore(equality1, edit)            + diff_cleanupSemanticScore(edit, equality2);        while (edit.length() != 0 && equality2.length() != 0            && edit.charAt(0) == equality2.charAt(0)) {          equality1 += edit.charAt(0);          edit = edit.substring(1) + equality2.charAt(0);          equality2 = equality2.substring(1);          score = diff_cleanupSemanticScore(equality1, edit)              + diff_cleanupSemanticScore(edit, equality2);          // The >= encourages trailing rather than leading whitespace on edits.          if (score >= bestScore) {            bestScore = score;            bestEquality1 = equality1;            bestEdit = edit;            bestEquality2 = equality2;          }        }        if (!prevDiff.text.equals(bestEquality1)) {          // We have an improvement, save it back to the diff.          if (bestEquality1.length() != 0) {            prevDiff.text = bestEquality1;          } else {            pointer.previous(); // Walk past nextDiff.            pointer.previous(); // Walk past thisDiff.            pointer.previous(); // Walk past prevDiff.            pointer.remove(); // Delete prevDiff.            pointer.next(); // Walk past thisDiff.            pointer.next(); // Walk past nextDiff.          }          thisDiff.text = bestEdit;          if (bestEquality2.length() != 0) {            nextDiff.text = bestEquality2;          } else {            pointer.remove(); // Delete nextDiff.            nextDiff = thisDiff;            thisDiff = prevDiff;          }        }      }      prevDiff = thisDiff;      thisDiff = nextDiff;      nextDiff = pointer.hasNext() ? pointer.next() : null;    }  }  /**   * Given two strings, compute a score representing whether the internal   * boundary falls on logical boundaries.   * Scores range from 5 (best) to 0 (worst).   * @param one First string.   * @param two Second string.   * @return The score.   */  private int diff_cleanupSemanticScore(String one, String two) {    if (one.length() == 0 || two.length() == 0) {      // Edges are the best.      return 5;    }    // Each port of this function behaves slightly differently due to    // subtle differences in each language's definition of things like    // 'whitespace'.  Since this function's purpose is largely cosmetic,    // the choice has been made to use each language's native features    // rather than force total conformity.    int score = 0;    // One point for non-alphanumeric.    if (!Character.isLetterOrDigit(one.charAt(one.length() - 1))        || !Character.isLetterOrDigit(two.charAt(0))) {      score++;      // Two points for whitespace.      if (Character.isWhitespace(one.charAt(one.length() - 1))          || Character.isWhitespace(two.charAt(0))) {        score++;        // Three points for line breaks.        if (Character.getType(one.charAt(one.length() - 1)) == Character.CONTROL            || Character.getType(two.charAt(0)) == Character.CONTROL) {          score++;          // Four points for blank lines.          if (BLANKLINEEND.matcher(one).find()              || BLANKLINESTART.matcher(two).find()) {            score++;          }        }      }    }    return score;  }  private Pattern BLANKLINEEND      = Pattern.compile("\\n\\r?\\n\\Z", Pattern.DOTALL);  private Pattern BLANKLINESTART      = Pattern.compile("\\A\\r?\\n\\r?\\n", Pattern.DOTALL);  /**   * Reduce the number of edits by eliminating operationally trivial equalities.   * @param diffs LinkedList of Diff objects.   */  public void diff_cleanupEfficiency(LinkedList<Diff> diffs) {    if (diffs.isEmpty()) {      return;    }    boolean changes = false;    Stack<Diff> equalities = new Stack<Diff>();  // Stack of equalities.    String lastequality = null; // Always equal to equalities.lastElement().text    ListIterator<Diff> pointer = diffs.listIterator();    // Is there an insertion operation before the last equality.    boolean pre_ins = false;    // Is there a deletion operation before the last equality.    boolean pre_del = false;    // Is there an insertion operation after the last equality.    boolean post_ins = false;    // Is there a deletion operation after the last equality.    boolean post_del = false;    Diff thisDiff = pointer.next();    Diff safeDiff = thisDiff;  // The last Diff that is known to be unsplitable.    while (thisDiff != null) {      if (thisDiff.operation == Operation.EQUAL) {        // equality found        if (thisDiff.text.length() < Diff_EditCost && (post_ins || post_del)) {          // Candidate found.          equalities.push(thisDiff);          pre_ins = post_ins;          pre_del = post_del;          lastequality = thisDiff.text;        } else {          // Not a candidate, and can never become one.          equalities.clear();          lastequality = null;          safeDiff = thisDiff;        }        post_ins = post_del = false;      } else {        // an insertion or deletion        if (thisDiff.operation == Operation.DELETE) {          post_del = true;        } else {          post_ins = true;        }        /*         * Five types to be split:         * <ins>A</ins><del>B</del>XY<ins>C</ins><del>D</del>         * <ins>A</ins>X<ins>C</ins><del>D</del>         * <ins>A</ins><del>B</del>X<ins>C</ins>         * <ins>A</del>X<ins>C</ins><del>D</del>         * <ins>A</ins><del>B</del>X<del>C</del>         */        if (lastequality != null            && ((pre_ins && pre_del && post_ins && post_del)                || ((lastequality.length() < Diff_EditCost / 2)                    && ((pre_ins ? 1 : 0) + (pre_del ? 1 : 0)                        + (post_ins ? 1 : 0) + (post_del ? 1 : 0)) == 3))) {          //System.out.println("Splitting: '" + lastequality + "'");          // Walk back to offending equality.          while (thisDiff != equalities.lastElement()) {            thisDiff = pointer.previous();          }          pointer.next();          // Replace equality with a delete.          pointer.set(new Diff(Operation.DELETE, lastequality));          // Insert a corresponding an insert.          pointer.add(thisDiff = new Diff(Operation.INSERT, lastequality));          equalities.pop();  // Throw away the equality we just deleted.          lastequality = null;          if (pre_ins && pre_del) {            // No changes made which could affect previous entry, keep going.            post_ins = post_del = true;            equalities.clear();            safeDiff = thisDiff;          } else {            if (!equalities.empty()) {              // Throw away the previous equality (it needs to be reevaluated).              equalities.pop();            }            if (equalities.empty()) {              // There are no previous questionable equalities,              // walk back to the last known safe diff.              thisDiff = safeDiff;            } else {              // There is an equality we can fall back to.              thisDiff = equalities.lastElement();            }            while (thisDiff != pointer.previous()) {              // Intentionally empty loop.            }            post_ins = post_del = false;          }          changes = true;        }      }      thisDiff = pointer.hasNext() ? pointer.next() : null;    }    if (changes) {      diff_cleanupMerge(diffs);    }  }  /**   * Reorder and merge like edit sections.  Merge equalities.   * Any edit section can move as long as it doesn't cross an equality.   * @param diffs LinkedList of Diff objects.   */  public void diff_cleanupMerge(LinkedList<Diff> diffs) {    diffs.add(new Diff(Operation.EQUAL, ""));  // Add a dummy entry at the end.    ListIterator<Diff> pointer = diffs.listIterator();    int count_delete = 0;    int count_insert = 0;    String text_delete = "";    String text_insert = "";    Diff thisDiff = pointer.next();    Diff prevEqual = null;    int commonlength;    while (thisDiff != null) {      switch (thisDiff.operation) {      case INSERT:        count_insert++;        text_insert += thisDiff.text;        prevEqual = null;        break;      case DELETE:        count_delete++;        text_delete += thisDiff.text;        prevEqual = null;        break;      case EQUAL:        if (count_delete != 0 || count_insert != 0) {          // Delete the offending records.          pointer.previous();  // Reverse direction.          while (count_delete-- > 0) {            pointer.previous();            pointer.remove();          }          while (count_insert-- > 0) {            pointer.previous();            pointer.remove();          }          if (count_delete != 0 && count_insert != 0) {            // Factor out any common prefixies.            commonlength = diff_commonPrefix(text_insert, text_delete);            if (commonlength != 0) {              if (pointer.hasPrevious()) {                thisDiff = pointer.previous();                assert thisDiff.operation == Operation.EQUAL                       : "Previous diff should have been an equality.";                thisDiff.text += text_insert.substring(0, commonlength);                pointer.next();              } else {                pointer.add(new Diff(Operation.EQUAL,                    text_insert.substring(0, commonlength)));              }              text_insert = text_insert.substring(commonlength);              text_delete = text_delete.substring(commonlength);            }            // Factor out any common suffixies.            commonlength = diff_commonSuffix(text_insert, text_delete);            if (commonlength != 0) {              thisDiff = pointer.next();              thisDiff.text = text_insert.substring(text_insert.length()                  - commonlength) + thisDiff.text;              text_insert = text_insert.substring(0, text_insert.length()                  - commonlength);              text_delete = text_delete.substring(0, text_delete.length()                  - commonlength);              pointer.previous();            }          }          // Insert the merged records.          if (text_delete.length() != 0) {            pointer.add(new Diff(Operation.DELETE, text_delete));          }          if (text_insert.length() != 0) {            pointer.add(new Diff(Operation.INSERT, text_insert));          }          // Step forward to the equality.          thisDiff = pointer.hasNext() ? pointer.next() : null;        } else if (prevEqual != null) {          // Merge this equality with the previous one.          prevEqual.text += thisDiff.text;          pointer.remove();          thisDiff = pointer.previous();          pointer.next();  // Forward direction        }        count_insert = 0;        count_delete = 0;        text_delete = "";        text_insert = "";        prevEqual = thisDiff;        break;      }      thisDiff = pointer.hasNext() ? pointer.next() : null;    }    // System.out.println(diff);    if (diffs.getLast().text.length() == 0) {      diffs.removeLast();  // Remove the dummy entry at the end.    }    /*     * Second pass: look for single edits surrounded on both sides by equalities     * which can be shifted sideways to eliminate an equality.     * e.g: A<ins>BA</ins>C -> <ins>AB</ins>AC     */    boolean changes = false;    // Create a new iterator at the start.    // (As opposed to walking the current one back.)    pointer = diffs.listIterator();    Diff prevDiff = pointer.hasNext() ? pointer.next() : null;    thisDiff = pointer.hasNext() ? pointer.next() : null;    Diff nextDiff = pointer.hasNext() ? pointer.next() : null;    // Intentionally ignore the first and last element (don't need checking).    while (nextDiff != null) {      if (prevDiff.operation == Operation.EQUAL &&          nextDiff.operation == Operation.EQUAL) {        // This is a single edit surrounded by equalities.        if (thisDiff.text.endsWith(prevDiff.text)) {          // Shift the edit over the previous equality.          thisDiff.text = prevDiff.text + thisDiff.text.substring(0, thisDiff.text.length() - prevDiff.text.length());          nextDiff.text = prevDiff.text + nextDiff.text;          pointer.previous(); // Walk past nextDiff.          pointer.previous(); // Walk past thisDiff.          pointer.previous(); // Walk past prevDiff.          pointer.remove(); // Delete prevDiff.          pointer.next(); // Walk past thisDiff.          thisDiff = pointer.next(); // Walk past nextDiff.          nextDiff = pointer.hasNext() ? pointer.next() : null;          changes = true;        } else if (thisDiff.text.startsWith(nextDiff.text)) {          // Shift the edit over the next equality.          prevDiff.text += nextDiff.text;          thisDiff.text = thisDiff.text.substring(nextDiff.text.length())              + nextDiff.text;          pointer.remove(); // Delete nextDiff.          nextDiff = pointer.hasNext() ? pointer.next() : null;          changes = true;        }      }      prevDiff = thisDiff;      thisDiff = nextDiff;      nextDiff = pointer.hasNext() ? pointer.next() : null;    }    // If shifts were made, the diff needs reordering and another shift sweep.    if (changes) {      diff_cleanupMerge(diffs);    }  }  /**   * loc is a location in text1, compute and return the equivalent location in   * text2.   * e.g. "The cat" vs "The big cat", 1->1, 5->8   * @param diffs LinkedList of Diff objects.   * @param loc Location within text1.   * @return Location within text2.   */  public int diff_xIndex(LinkedList<Diff> diffs, int loc) {    int chars1 = 0;    int chars2 = 0;    int last_chars1 = 0;    int last_chars2 = 0;    Diff lastDiff = null;    for (Diff aDiff : diffs) {      if (aDiff.operation != Operation.INSERT) {        // Equality or deletion.        chars1 += aDiff.text.length();      }      if (aDiff.operation != Operation.DELETE) {        // Equality or insertion.        chars2 += aDiff.text.length();      }      if (chars1 > loc) {        // Overshot the location.        lastDiff = aDiff;        break;      }      last_chars1 = chars1;      last_chars2 = chars2;    }    if (lastDiff != null && lastDiff.operation == Operation.DELETE) {      // The location was deleted.      return last_chars2;    }    // Add the remaining character length.    return last_chars2 + (loc - last_chars1);  }  /**   * Convert a Diff list into a pretty HTML report.   * @param diffs LinkedList of Diff objects.   * @return HTML representation.   */  public String diff_prettyHtml(LinkedList<Diff> diffs) {    StringBuilder html = new StringBuilder();    int i = 0;    for (Diff aDiff : diffs) {      String text = aDiff.text.replace("&", "&amp;").replace("<", "&lt;")          .replace(">", "&gt;").replace("\n", "&para;<BR>");      switch (aDiff.operation) {      case INSERT:        html.append("<INS STYLE=\"background:#E6FFE6;\" TITLE=\"i=").append(i)            .append("\">").append(text).append("</INS>");        break;      case DELETE:        html.append("<DEL STYLE=\"background:#FFE6E6;\" TITLE=\"i=").append(i)            .append("\">").append(text).append("</DEL>");        break;      case EQUAL:        html.append("<SPAN TITLE=\"i=").append(i).append("\">").append(text)            .append("</SPAN>");        break;      }      if (aDiff.operation != Operation.DELETE) {        i += aDiff.text.length();      }    }    return html.toString();  }  /**   * Compute and return the source text (all equalities and deletions).   * @param diffs LinkedList of Diff objects.   * @return Source text.   */  public String diff_text1(LinkedList<Diff> diffs) {    StringBuilder text = new StringBuilder();    for (Diff aDiff : diffs) {      if (aDiff.operation != Operation.INSERT) {        text.append(aDiff.text);      }    }    return text.toString();  }  /**   * Compute and return the destination text (all equalities and insertions).   * @param diffs LinkedList of Diff objects.   * @return Destination text.   */  public String diff_text2(LinkedList<Diff> diffs) {    StringBuilder text = new StringBuilder();    for (Diff aDiff : diffs) {      if (aDiff.operation != Operation.DELETE) {        text.append(aDiff.text);      }    }    return text.toString();  }  /**   * Compute the Levenshtein distance; the number of inserted, deleted or   * substituted characters.   * @param diffs LinkedList of Diff objects.   * @return Number of changes.   */  public int diff_levenshtein(LinkedList<Diff> diffs) {    int levenshtein = 0;    int insertions = 0;    int deletions = 0;    for (Diff aDiff : diffs) {      switch (aDiff.operation) {      case INSERT:        insertions += aDiff.text.length();        break;      case DELETE:        deletions += aDiff.text.length();        break;      case EQUAL:        // A deletion and an insertion is one substitution.        levenshtein += Math.max(insertions, deletions);        insertions = 0;        deletions = 0;        break;      }    }    levenshtein += Math.max(insertions, deletions);    return levenshtein;  }  /**   * Crush the diff into an encoded string which describes the operations   * required to transform text1 into text2.   * E.g. =3\t-2\t+ing  -> Keep 3 chars, delete 2 chars, insert 'ing'.   * Operations are tab-separated.  Inserted text is escaped using %xx notation.   * @param diffs Array of diff tuples.   * @return Delta text.   */  public String diff_toDelta(LinkedList<Diff> diffs) {    StringBuilder text = new StringBuilder();    for (Diff aDiff : diffs) {      switch (aDiff.operation) {      case INSERT:        try {          text.append("+").append(URLEncoder.encode(aDiff.text, "UTF-8")                                            .replace('+', ' ')).append("\t");        } catch (UnsupportedEncodingException e) {          // Not likely on modern system.          throw new Error("This system does not support UTF-8.", e);        }        break;      case DELETE:        text.append("-").append(aDiff.text.length()).append("\t");        break;      case EQUAL:        text.append("=").append(aDiff.text.length()).append("\t");        break;      }    }    String delta = text.toString();    if (delta.length() != 0) {      // Strip off trailing tab character.      delta = delta.substring(0, delta.length() - 1);      delta = unescapeForEncodeUriCompatability(delta);    }    return delta;  }  /**   * Given the original text1, and an encoded string which describes the   * operations required to transform text1 into text2, compute the full diff.   * @param text1 Source string for the diff.   * @param delta Delta text.   * @return Array of diff tuples or null if invalid.   * @throws IllegalArgumentException If invalid input.   */  public LinkedList<Diff> diff_fromDelta(String text1, String delta)      throws IllegalArgumentException {    LinkedList<Diff> diffs = new LinkedList<Diff>();    int pointer = 0;  // Cursor in text1    String[] tokens = delta.split("\t");    for (String token : tokens) {      if (token.length() == 0) {        // Blank tokens are ok (from a trailing \t).        continue;      }      // Each token begins with a one character parameter which specifies the      // operation of this token (delete, insert, equality).      String param = token.substring(1);      switch (token.charAt(0)) {      case '+':        // decode would change all "+" to " "        param = param.replace("+", "%2B");        try {          param = URLDecoder.decode(param, "UTF-8");        } catch (UnsupportedEncodingException e) {          // Not likely on modern system.          throw new Error("This system does not support UTF-8.", e);        } catch (IllegalArgumentException e) {          // Malformed URI sequence.          throw new IllegalArgumentException(              "Illegal escape in diff_fromDelta: " + param, e);        }        diffs.add(new Diff(Operation.INSERT, param));        break;      case '-':        // Fall through.      case '=':        int n;        try {          n = Integer.parseInt(param);        } catch (NumberFormatException e) {          throw new IllegalArgumentException(              "Invalid number in diff_fromDelta: " + param, e);        }        if (n < 0) {          throw new IllegalArgumentException(              "Negative number in diff_fromDelta: " + param);        }        String text;        try {          text = text1.substring(pointer, pointer += n);        } catch (StringIndexOutOfBoundsException e) {          throw new IllegalArgumentException("Delta length (" + pointer              + ") larger than source text length (" + text1.length()              + ").", e);        }        if (token.charAt(0) == '=') {          diffs.add(new Diff(Operation.EQUAL, text));        } else {          diffs.add(new Diff(Operation.DELETE, text));        }        break;      default:        // Anything else is an error.        throw new IllegalArgumentException(            "Invalid diff operation in diff_fromDelta: " + token.charAt(0));      }    }    if (pointer != text1.length()) {      throw new IllegalArgumentException("Delta length (" + pointer          + ") smaller than source text length (" + text1.length() + ").");    }    return diffs;  }  //  MATCH FUNCTIONS  /**   * Locate the best instance of 'pattern' in 'text' near 'loc'.   * Returns -1 if no match found.   * @param text The text to search.   * @param pattern The pattern to search for.   * @param loc The location to search around.   * @return Best match index or -1.   */  public int match_main(String text, String pattern, int loc) {    loc = Math.max(0, Math.min(loc, text.length()));    if (text.equals(pattern)) {      // Shortcut (potentially not guaranteed by the algorithm)      return 0;    } else if (text.length() == 0) {      // Nothing to match.      return -1;    } else if (loc + pattern.length() <= text.length()        && text.substring(loc, loc + pattern.length()).equals(pattern)) {      // Perfect match at the perfect spot!  (Includes case of null pattern)      return loc;    } else {      // Do a fuzzy compare.      return match_bitap(text, pattern, loc);    }  }  /**   * Locate the best instance of 'pattern' in 'text' near 'loc' using the   * Bitap algorithm.  Returns -1 if no match found.   * @param text The text to search.   * @param pattern The pattern to search for.   * @param loc The location to search around.   * @return Best match index or -1.   */  protected int match_bitap(String text, String pattern, int loc) {    assert (Match_MaxBits == 0 || pattern.length() <= Match_MaxBits)        : "Pattern too long for this application.";    // Initialise the alphabet.    Map<Character, Integer> s = match_alphabet(pattern);    // Highest score beyond which we give up.    double score_threshold = Match_Threshold;    // Is there a nearby exact match? (speedup)    int best_loc = text.indexOf(pattern, loc);    if (best_loc != -1) {      score_threshold = Math.min(match_bitapScore(0, best_loc, loc, pattern),          score_threshold);      // What about in the other direction? (speedup)      best_loc = text.lastIndexOf(pattern, loc + pattern.length());      if (best_loc != -1) {        score_threshold = Math.min(match_bitapScore(0, best_loc, loc, pattern),            score_threshold);      }    }    // Initialise the bit arrays.    int matchmask = 1 << (pattern.length() - 1);    best_loc = -1;    int bin_min, bin_mid;    int bin_max = pattern.length() + text.length();    // Empty initialization added to appease Java compiler.    int[] last_rd = new int[0];    for (int d = 0; d < pattern.length(); d++) {      // Scan for the best match; each iteration allows for one more error.      // Run a binary search to determine how far from 'loc' we can stray at      // this error level.      bin_min = 0;      bin_mid = bin_max;      while (bin_min < bin_mid) {        if (match_bitapScore(d, loc + bin_mid, loc, pattern)            <= score_threshold) {          bin_min = bin_mid;        } else {          bin_max = bin_mid;        }        bin_mid = (bin_max - bin_min) / 2 + bin_min;      }      // Use the result from this iteration as the maximum for the next.      bin_max = bin_mid;      int start = Math.max(1, loc - bin_mid + 1);      int finish = Math.min(loc + bin_mid, text.length()) + pattern.length();      int[] rd = new int[finish + 2];      rd[finish + 1] = (1 << d) - 1;      for (int j = finish; j >= start; j--) {        int charMatch;        if (text.length() <= j - 1 || !s.containsKey(text.charAt(j - 1))) {          // Out of range.          charMatch = 0;        } else {          charMatch = s.get(text.charAt(j - 1));        }        if (d == 0) {          // First pass: exact match.          rd[j] = ((rd[j + 1] << 1) | 1) & charMatch;        } else {          // Subsequent passes: fuzzy match.          rd[j] = ((rd[j + 1] << 1) | 1) & charMatch              | (((last_rd[j + 1] | last_rd[j]) << 1) | 1) | last_rd[j + 1];        }        if ((rd[j] & matchmask) != 0) {          double score = match_bitapScore(d, j - 1, loc, pattern);          // This match will almost certainly be better than any existing          // match.  But check anyway.          if (score <= score_threshold) {            // Told you so.            score_threshold = score;            best_loc = j - 1;            if (best_loc > loc) {              // When passing loc, don't exceed our current distance from loc.              start = Math.max(1, 2 * loc - best_loc);            } else {              // Already passed loc, downhill from here on in.              break;            }          }        }      }      if (match_bitapScore(d + 1, loc, loc, pattern) > score_threshold) {        // No hope for a (better) match at greater error levels.        break;      }      last_rd = rd;    }    return best_loc;  }  /**   * Compute and return the score for a match with e errors and x location.   * @param e Number of errors in match.   * @param x Location of match.   * @param loc Expected location of match.   * @param pattern Pattern being sought.   * @return Overall score for match (0.0 = good, 1.0 = bad).   */  private double match_bitapScore(int e, int x, int loc, String pattern) {    float accuracy = (float) e / pattern.length();    int proximity = Math.abs(loc - x);    if (Match_Distance == 0) {      // Dodge divide by zero error.      return proximity == 0 ? accuracy : 1.0;    }    return accuracy + (proximity / (float) Match_Distance);  }  /**   * Initialise the alphabet for the Bitap algorithm.   * @param pattern The text to encode.   * @return Hash of character locations.   */  protected Map<Character, Integer> match_alphabet(String pattern) {    Map<Character, Integer> s = new HashMap<Character, Integer>();    char[] char_pattern = pattern.toCharArray();    for (char c : char_pattern) {      s.put(c, 0);    }    int i = 0;    for (char c : char_pattern) {      s.put(c, s.get(c) | (1 << (pattern.length() - i - 1)));      i++;    }    return s;  }  //  PATCH FUNCTIONS  /**   * Increase the context until it is unique,   * but don't let the pattern expand beyond Match_MaxBits.   * @param patch The patch to grow.   * @param text Source text.   */  protected void patch_addContext(Patch patch, String text) {    if (text.length() == 0) {      return;    }    String pattern = text.substring(patch.start2, patch.start2 + patch.length1);    int padding = 0;    // Look for the first and last matches of pattern in text.  If two different    // matches are found, increase the pattern length.    while (text.indexOf(pattern) != text.lastIndexOf(pattern)        && pattern.length() < Match_MaxBits - Patch_Margin - Patch_Margin) {      padding += Patch_Margin;      pattern = text.substring(Math.max(0, patch.start2 - padding),          Math.min(text.length(), patch.start2 + patch.length1 + padding));    }    // Add one chunk for good luck.    padding += Patch_Margin;    // Add the prefix.    String prefix = text.substring(Math.max(0, patch.start2 - padding),        patch.start2);    if (prefix.length() != 0) {      patch.diffs.addFirst(new Diff(Operation.EQUAL, prefix));    }    // Add the suffix.    String suffix = text.substring(patch.start2 + patch.length1,        Math.min(text.length(), patch.start2 + patch.length1 + padding));    if (suffix.length() != 0) {      patch.diffs.addLast(new Diff(Operation.EQUAL, suffix));    }    // Roll back the start points.    patch.start1 -= prefix.length();    patch.start2 -= prefix.length();    // Extend the lengths.    patch.length1 += prefix.length() + suffix.length();    patch.length2 += prefix.length() + suffix.length();  }  /**   * Compute a list of patches to turn text1 into text2.   * A set of diffs will be computed.   * @param text1 Old text.   * @param text2 New text.   * @return LinkedList of Patch objects.   */  public LinkedList<Patch> patch_make(String text1, String text2) {    // No diffs provided, compute our own.    LinkedList<Diff> diffs = diff_main(text1, text2, true);    if (diffs.size() > 2) {      diff_cleanupSemantic(diffs);      diff_cleanupEfficiency(diffs);    }    return patch_make(text1, diffs);  }  /**   * Compute a list of patches to turn text1 into text2.   * text1 will be derived from the provided diffs.   * @param diffs Array of diff tuples for text1 to text2.   * @return LinkedList of Patch objects.   */  public LinkedList<Patch> patch_make(LinkedList<Diff> diffs) {    // No origin string provided, compute our own.    String text1 = diff_text1(diffs);    return patch_make(text1, diffs);  }  /**   * Compute a list of patches to turn text1 into text2.   * text2 is ignored, diffs are the delta between text1 and text2.   * @param text1 Old text   * @param text2 Ignored.   * @param diffs Array of diff tuples for text1 to text2.   * @return LinkedList of Patch objects.   * @deprecated Prefer patch_make(String text1, LinkedList<Diff> diffs).   */  public LinkedList<Patch> patch_make(String text1, String text2,      LinkedList<Diff> diffs) {    return patch_make(text1, diffs);  }  /**   * Compute a list of patches to turn text1 into text2.   * text2 is not provided, diffs are the delta between text1 and text2.   * @param text1 Old text.   * @param diffs Array of diff tuples for text1 to text2.   * @return LinkedList of Patch objects.   */  public LinkedList<Patch> patch_make(String text1, LinkedList<Diff> diffs) {    LinkedList<Patch> patches = new LinkedList<Patch>();    if (diffs.isEmpty()) {      return patches;  // Get rid of the null case.    }    Patch patch = new Patch();    int char_count1 = 0;  // Number of characters into the text1 string.    int char_count2 = 0;  // Number of characters into the text2 string.    // Start with text1 (prepatch_text) and apply the diffs until we arrive at    // text2 (postpatch_text). We recreate the patches one by one to determine    // context info.    String prepatch_text = text1;    String postpatch_text = text1;    for (Diff aDiff : diffs) {      if (patch.diffs.isEmpty() && aDiff.operation != Operation.EQUAL) {        // A new patch starts here.        patch.start1 = char_count1;        patch.start2 = char_count2;      }      switch (aDiff.operation) {      case INSERT:        patch.diffs.add(aDiff);        patch.length2 += aDiff.text.length();        postpatch_text = postpatch_text.substring(0, char_count2)            + aDiff.text + postpatch_text.substring(char_count2);        break;      case DELETE:        patch.length1 += aDiff.text.length();        patch.diffs.add(aDiff);        postpatch_text = postpatch_text.substring(0, char_count2)            + postpatch_text.substring(char_count2 + aDiff.text.length());        break;      case EQUAL:        if (aDiff.text.length() <= 2 * Patch_Margin            && !patch.diffs.isEmpty() && aDiff != diffs.getLast()) {          // Small equality inside a patch.          patch.diffs.add(aDiff);          patch.length1 += aDiff.text.length();          patch.length2 += aDiff.text.length();        }        if (aDiff.text.length() >= 2 * Patch_Margin) {          // Time for a new patch.          if (!patch.diffs.isEmpty()) {            patch_addContext(patch, prepatch_text);            patches.add(patch);            patch = new Patch();            // Unlike Unidiff, our patch lists have a rolling context.            // http://code.google.com/p/google-diff-match-patch/wiki/Unidiff            // Update prepatch text & pos to reflect the application of the            // just completed patch.            prepatch_text = postpatch_text;            char_count1 = char_count2;          }        }        break;      }      // Update the current character count.      if (aDiff.operation != Operation.INSERT) {        char_count1 += aDiff.text.length();      }      if (aDiff.operation != Operation.DELETE) {        char_count2 += aDiff.text.length();      }    }    // Pick up the leftover patch if not empty.    if (!patch.diffs.isEmpty()) {      patch_addContext(patch, prepatch_text);      patches.add(patch);    }    return patches;  }  /**   * Given an array of patches, return another array that is identical.   * @param patches Array of patch objects.   * @return Array of patch objects.   */  public LinkedList<Patch> patch_deepCopy(LinkedList<Patch> patches) {    LinkedList<Patch> patchesCopy = new LinkedList<Patch>();    for (Patch aPatch : patches) {      Patch patchCopy = new Patch();      for (Diff aDiff : aPatch.diffs) {        Diff diffCopy = new Diff(aDiff.operation, aDiff.text);        patchCopy.diffs.add(diffCopy);      }      patchCopy.start1 = aPatch.start1;      patchCopy.start2 = aPatch.start2;      patchCopy.length1 = aPatch.length1;      patchCopy.length2 = aPatch.length2;      patchesCopy.add(patchCopy);    }    return patchesCopy;  }  /**   * Merge a set of patches onto the text.  Return a patched text, as well   * as an array of true/false values indicating which patches were applied.   * @param patches Array of patch objects   * @param text Old text.   * @return Two element Object array, containing the new text and an array of   *      boolean values.   */  public Object[] patch_apply(LinkedList<Patch> patches, String text) {    if (patches.isEmpty()) {      return new Object[]{text, new boolean[0]};    }    // Deep copy the patches so that no changes are made to originals.    patches = patch_deepCopy(patches);    String nullPadding = patch_addPadding(patches);    text = nullPadding + text + nullPadding;    patch_splitMax(patches);    int x = 0;    // delta keeps track of the offset between the expected and actual location    // of the previous patch.  If there are patches expected at positions 10 and    // 20, but the first patch was found at 12, delta is 2 and the second patch    // has an effective expected position of 22.    int delta = 0;    boolean[] results = new boolean[patches.size()];    for (Patch aPatch : patches) {      int expected_loc = aPatch.start2 + delta;      String text1 = diff_text1(aPatch.diffs);      int start_loc;      int end_loc = -1;      if (text1.length() > this.Match_MaxBits) {        // patch_splitMax will only provide an oversized pattern in the case of        // a monster delete.        start_loc = match_main(text,            text1.substring(0, this.Match_MaxBits), expected_loc);        if (start_loc != -1) {          end_loc = match_main(text,              text1.substring(text1.length() - this.Match_MaxBits),              expected_loc + text1.length() - this.Match_MaxBits);          if (end_loc == -1 || start_loc >= end_loc) {            // Can't find valid trailing context.  Drop this patch.            start_loc = -1;          }        }      } else {        start_loc = match_main(text, text1, expected_loc);      }      if (start_loc == -1) {        // No match found.  :(        results[x] = false;        // Subtract the delta for this failed patch from subsequent patches.        delta -= aPatch.length2 - aPatch.length1;      } else {        // Found a match.  :)        results[x] = true;        delta = start_loc - expected_loc;        String text2;        if (end_loc == -1) {          text2 = text.substring(start_loc,              Math.min(start_loc + text1.length(), text.length()));        } else {          text2 = text.substring(start_loc,              Math.min(end_loc + this.Match_MaxBits, text.length()));        }        if (text1.equals(text2)) {          // Perfect match, just shove the replacement text in.          text = text.substring(0, start_loc) + diff_text2(aPatch.diffs)              + text.substring(start_loc + text1.length());        } else {          // Imperfect match.  Run a diff to get a framework of equivalent          // indices.          LinkedList<Diff> diffs = diff_main(text1, text2, false);          if (text1.length() > this.Match_MaxBits              && diff_levenshtein(diffs) / (float) text1.length()              > this.Patch_DeleteThreshold) {            // The end points match, but the content is unacceptably bad.            results[x] = false;          } else {            diff_cleanupSemanticLossless(diffs);            int index1 = 0;            for (Diff aDiff : aPatch.diffs) {              if (aDiff.operation != Operation.EQUAL) {                int index2 = diff_xIndex(diffs, index1);                if (aDiff.operation == Operation.INSERT) {                  // Insertion                  text = text.substring(0, start_loc + index2) + aDiff.text                      + text.substring(start_loc + index2);                } else if (aDiff.operation == Operation.DELETE) {                  // Deletion                  text = text.substring(0, start_loc + index2)                      + text.substring(start_loc + diff_xIndex(diffs,                      index1 + aDiff.text.length()));                }              }              if (aDiff.operation != Operation.DELETE) {                index1 += aDiff.text.length();              }            }          }        }      }      x++;    }    // Strip the padding off.    text = text.substring(nullPadding.length(), text.length()        - nullPadding.length());    return new Object[]{text, results};  }  /**   * Add some padding on text start and end so that edges can match something.   * Intended to be called only from within patch_apply.   * @param patches Array of patch objects.   * @return The padding string added to each side.   */  public String patch_addPadding(LinkedList<Patch> patches) {    int paddingLength = this.Patch_Margin;    String nullPadding = "";    for (int x = 1; x <= paddingLength; x++) {      nullPadding += String.valueOf((char) x);    }    // Bump all the patches forward.    for (Patch aPatch : patches) {      aPatch.start1 += paddingLength;      aPatch.start2 += paddingLength;    }    // Add some padding on start of first diff.    Patch patch = patches.getFirst();    LinkedList<Diff> diffs = patch.diffs;    if (diffs.isEmpty() || diffs.getFirst().operation != Operation.EQUAL) {      // Add nullPadding equality.      diffs.addFirst(new Diff(Operation.EQUAL, nullPadding));      patch.start1 -= paddingLength;  // Should be 0.      patch.start2 -= paddingLength;  // Should be 0.      patch.length1 += paddingLength;      patch.length2 += paddingLength;    } else if (paddingLength > diffs.getFirst().text.length()) {      // Grow first equality.      Diff firstDiff = diffs.getFirst();      int extraLength = paddingLength - firstDiff.text.length();      firstDiff.text = nullPadding.substring(firstDiff.text.length())          + firstDiff.text;      patch.start1 -= extraLength;      patch.start2 -= extraLength;      patch.length1 += extraLength;      patch.length2 += extraLength;    }    // Add some padding on end of last diff.    patch = patches.getLast();    diffs = patch.diffs;    if (diffs.isEmpty() || diffs.getLast().operation != Operation.EQUAL) {      // Add nullPadding equality.      diffs.addLast(new Diff(Operation.EQUAL, nullPadding));      patch.length1 += paddingLength;      patch.length2 += paddingLength;    } else if (paddingLength > diffs.getLast().text.length()) {      // Grow last equality.      Diff lastDiff = diffs.getLast();      int extraLength = paddingLength - lastDiff.text.length();      lastDiff.text += nullPadding.substring(0, extraLength);      patch.length1 += extraLength;      patch.length2 += extraLength;    }    return nullPadding;  }  /**   * Look through the patches and break up any which are longer than the   * maximum limit of the match algorithm.   * @param patches LinkedList of Patch objects.   */  public void patch_splitMax(LinkedList<Patch> patches) {    int patch_size;    String precontext, postcontext;    Patch patch;    int start1, start2;    boolean empty;    Operation diff_type;    String diff_text;    ListIterator<Patch> pointer = patches.listIterator();    Patch bigpatch = pointer.hasNext() ? pointer.next() : null;    while (bigpatch != null) {      if (bigpatch.length1 <= Match_MaxBits) {        bigpatch = pointer.hasNext() ? pointer.next() : null;        continue;      }      // Remove the big old patch.      pointer.remove();      patch_size = Match_MaxBits;      start1 = bigpatch.start1;      start2 = bigpatch.start2;      precontext = "";      while (!bigpatch.diffs.isEmpty()) {        // Create one of several smaller patches.        patch = new Patch();        empty = true;        patch.start1 = start1 - precontext.length();        patch.start2 = start2 - precontext.length();        if (precontext.length() != 0) {          patch.length1 = patch.length2 = precontext.length();          patch.diffs.add(new Diff(Operation.EQUAL, precontext));        }        while (!bigpatch.diffs.isEmpty()            && patch.length1 < patch_size - Patch_Margin) {          diff_type = bigpatch.diffs.getFirst().operation;          diff_text = bigpatch.diffs.getFirst().text;          if (diff_type == Operation.INSERT) {            // Insertions are harmless.            patch.length2 += diff_text.length();            start2 += diff_text.length();            patch.diffs.addLast(bigpatch.diffs.removeFirst());            empty = false;          } else if (diff_type == Operation.DELETE && patch.diffs.size() == 1              && patch.diffs.getFirst().operation == Operation.EQUAL              && diff_text.length() > 2 * patch_size) {            // This is a large deletion.  Let it pass in one chunk.            patch.length1 += diff_text.length();            start1 += diff_text.length();            empty = false;            patch.diffs.add(new Diff(diff_type, diff_text));            bigpatch.diffs.removeFirst();          } else {            // Deletion or equality.  Only take as much as we can stomach.            diff_text = diff_text.substring(0, Math.min(diff_text.length(),                patch_size - patch.length1 - Patch_Margin));            patch.length1 += diff_text.length();            start1 += diff_text.length();            if (diff_type == Operation.EQUAL) {              patch.length2 += diff_text.length();              start2 += diff_text.length();            } else {              empty = false;            }            patch.diffs.add(new Diff(diff_type, diff_text));            if (diff_text.equals(bigpatch.diffs.getFirst().text)) {              bigpatch.diffs.removeFirst();            } else {              bigpatch.diffs.getFirst().text = bigpatch.diffs.getFirst().text                  .substring(diff_text.length());            }          }        }        // Compute the head context for the next patch.        precontext = diff_text2(patch.diffs);        precontext = precontext.substring(Math.max(0, precontext.length()            - Patch_Margin));        // Append the end context for this patch.        if (diff_text1(bigpatch.diffs).length() > Patch_Margin) {          postcontext = diff_text1(bigpatch.diffs).substring(0, Patch_Margin);        } else {          postcontext = diff_text1(bigpatch.diffs);        }        if (postcontext.length() != 0) {          patch.length1 += postcontext.length();          patch.length2 += postcontext.length();          if (!patch.diffs.isEmpty()              && patch.diffs.getLast().operation == Operation.EQUAL) {            patch.diffs.getLast().text += postcontext;          } else {            patch.diffs.add(new Diff(Operation.EQUAL, postcontext));          }        }        if (!empty) {          pointer.add(patch);        }      }      bigpatch = pointer.hasNext() ? pointer.next() : null;    }  }  /**   * Take a list of patches and return a textual representation.   * @param patches List of Patch objects.   * @return Text representation of patches.   */  public String patch_toText(List<Patch> patches) {    StringBuilder text = new StringBuilder();    for (Patch aPatch : patches) {      text.append(aPatch);    }    return text.toString();  }  /**   * Parse a textual representation of patches and return a List of Patch   * objects.   * @param textline Text representation of patches.   * @return List of Patch objects.   * @throws IllegalArgumentException If invalid input.   */  public List<Patch> patch_fromText(String textline)      throws IllegalArgumentException {    List<Patch> patches = new LinkedList<Patch>();    if (textline.length() == 0) {      return patches;    }    List<String> textList = Arrays.asList(textline.split("\n"));    LinkedList<String> text = new LinkedList<String>(textList);    Patch patch;    Pattern patchHeader        = Pattern.compile("^@@ -(\\d+),?(\\d*) \\+(\\d+),?(\\d*) @@$");    Matcher m;    char sign;    String line;    while (!text.isEmpty()) {      m = patchHeader.matcher(text.getFirst());      if (!m.matches()) {        throw new IllegalArgumentException(            "Invalid patch string: " + text.getFirst());      }      patch = new Patch();      patches.add(patch);      patch.start1 = Integer.parseInt(m.group(1));      if (m.group(2).length() == 0) {        patch.start1--;        patch.length1 = 1;      } else if (m.group(2).equals("0")) {        patch.length1 = 0;      } else {        patch.start1--;        patch.length1 = Integer.parseInt(m.group(2));      }      patch.start2 = Integer.parseInt(m.group(3));      if (m.group(4).length() == 0) {        patch.start2--;        patch.length2 = 1;      } else if (m.group(4).equals("0")) {        patch.length2 = 0;      } else {        patch.start2--;        patch.length2 = Integer.parseInt(m.group(4));      }      text.removeFirst();      while (!text.isEmpty()) {        try {          sign = text.getFirst().charAt(0);        } catch (IndexOutOfBoundsException e) {          // Blank line?  Whatever.          text.removeFirst();          continue;        }        line = text.getFirst().substring(1);        line = line.replace("+", "%2B");  // decode would change all "+" to " "        try {          line = URLDecoder.decode(line, "UTF-8");        } catch (UnsupportedEncodingException e) {          // Not likely on modern system.          throw new Error("This system does not support UTF-8.", e);        } catch (IllegalArgumentException e) {          // Malformed URI sequence.          throw new IllegalArgumentException(              "Illegal escape in patch_fromText: " + line, e);        }        if (sign == '-') {          // Deletion.          patch.diffs.add(new Diff(Operation.DELETE, line));        } else if (sign == '+') {          // Insertion.          patch.diffs.add(new Diff(Operation.INSERT, line));        } else if (sign == ' ') {          // Minor equality.          patch.diffs.add(new Diff(Operation.EQUAL, line));        } else if (sign == '@') {          // Start of next patch.          break;        } else {          // WTF?          throw new IllegalArgumentException(              "Invalid patch mode '" + sign + "' in: " + line);        }        text.removeFirst();      }    }    return patches;  }  /**   * Class representing one diff operation.   */  public static class Diff {    /**     * One of: INSERT, DELETE or EQUAL.     */    public Operation operation;    /**     * The text associated with this diff operation.     */    public String text;    /**     * Constructor.  Initializes the diff with the provided values.     * @param operation One of INSERT, DELETE or EQUAL.     * @param text The text being applied.     */    public Diff(Operation operation, String text) {      // Construct a diff with the specified operation and text.      this.operation = operation;      this.text = text;    }    /**     * Display a human-readable version of this Diff.     * @return text version.     */    public String toString() {      String prettyText = this.text.replace('\n', '\u00b6');      return "Diff(" + this.operation + ",\"" + prettyText + "\")";    }    /**     * Is this Diff equivalent to another Diff?     * @param d Another Diff to compare against.     * @return true or false.     */    public boolean equals(Object d) {      try {        return (((Diff) d).operation == this.operation)               && (((Diff) d).text.equals(this.text));      } catch (ClassCastException e) {        return false;      }    }  }  /**   * Class representing one patch operation.   */  public static class Patch {    public LinkedList<Diff> diffs;    public int start1;    public int start2;    public int length1;    public int length2;    /**     * Constructor.  Initializes with an empty list of diffs.     */    public Patch() {      this.diffs = new LinkedList<Diff>();    }    /**     * Emmulate GNU diff's format.     * Header: @@ -382,8 +481,9 @@     * Indicies are printed as 1-based, not 0-based.     * @return The GNU diff string.     */    public String toString() {      String coords1, coords2;      if (this.length1 == 0) {        coords1 = this.start1 + ",0";      } else if (this.length1 == 1) {        coords1 = Integer.toString(this.start1 + 1);      } else {        coords1 = (this.start1 + 1) + "," + this.length1;      }      if (this.length2 == 0) {        coords2 = this.start2 + ",0";      } else if (this.length2 == 1) {        coords2 = Integer.toString(this.start2 + 1);      } else {        coords2 = (this.start2 + 1) + "," + this.length2;      }      StringBuilder text = new StringBuilder();      text.append("@@ -").append(coords1).append(" +").append(coords2)          .append(" @@\n");      // Escape the body of the patch with %xx notation.      for (Diff aDiff : this.diffs) {        switch (aDiff.operation) {        case INSERT:          text.append('+');          break;        case DELETE:          text.append('-');          break;        case EQUAL:          text.append(' ');          break;        }        try {          text.append(URLEncoder.encode(aDiff.text, "UTF-8").replace('+', ' '))              .append("\n");        } catch (UnsupportedEncodingException e) {          // Not likely on modern system.          throw new Error("This system does not support UTF-8.", e);        }      }      return unescapeForEncodeUriCompatability(text.toString());    }  }  /**   * Unescape selected chars for compatability with JavaScript's encodeURI.   * In speed critical applications this could be dropped since the   * receiving application will certainly decode these fine.   * Note that this function is case-sensitive.  Thus "%3f" would not be   * unescaped.  But this is ok because it is only called with the output of   * URLEncoder.encode which returns uppercase hex.   *   * Example: "%3F" -> "?", "%24" -> "$", etc.   *   * @param str The string to escape.   * @return The escaped string.   */  private static String unescapeForEncodeUriCompatability(String str) {    return str.replace("%21", "!").replace("%7E", "~")        .replace("%27", "'").replace("%28", "(").replace("%29", ")")        .replace("%3B", ";").replace("%2F", "/").replace("%3F", "?")        .replace("%3A", ":").replace("%40", "@").replace("%26", "&")        .replace("%3D", "=").replace("%2B", "+").replace("%24", "$")        .replace("%2C", ",").replace("%23", "#");  }  public  String getHtmlDiffString(String text1,String text2){      return diff_prettyHtml(diff_main(text1,text2));   }  public static void main(String[] args){      Diff_match_patch dmp = new Diff_match_patch();       String text1 = "我方在“福市财政资金补助项目管理系统”的项目实施过程，为保证该项目的工程进度、质量，符合数办项目的实施管理规范与要求。";      String text2 = "我方在“福州市财政资金补助项目管理系统”的项目实施过程，为保证该haha项目的工程进度、质量，符合目的实施管理规范与要求。";      System.out.println(dmp.getHtmlDiffString(text1,text2));  }}