Java常用的字符串操作

//字符串搜索最后出现的位置这个例子显示了使用strOrig.lastIndexOf(Stringname) 方法如何确定一个字符串里面的子字符串的最后一个位置。public class SearchlastString{public static void main(String[] args){String strOrig="Hello world,Hello Reader";int lastIndex=strOrig.lastIndexOf("Hello");if(lastIndex==-1){System.out.println("Hello not found!");}elseSystem.out.println("Last occurence of Hello is at index"+lastIndex);}}//字符串比较下面的示例比较两个字符串用 str.compareTo (string) , str.compareToIgnoreCase(String) 和 str.compareTo(object string)，并返回字符串比较的第一个奇字的ascii不同。public class StringCompareEmp{   public static void main(String args[]){      String str = "Hello World";      String anotherString = "hello world";      Object objStr = str;      System.out.println( str.compareTo(anotherString) );      System.out.println( str.compareToIgnoreCase(anotherString) );      System.out.println( str.compareTo(objStr.toString()));   }}//字符串删除下面的例子演示了使用removeCharAt(string,position) 方法如何从一个字符串特定位置删除一个字符。java中substring的用法str＝str.substring(int beginIndex);截取掉str从首字母起长度为beginIndex的字符串，将剩余字符串赋值给str；str＝str.substring(int beginIndex，int endIndex);截取str中从beginIndex开始至endIndex结束时的字符串，并将其赋值给str;public class Main {   public static void main(String args[]) {      String str = "this is Java";      System.out.println(removeCharAt(str, 3));   }   public static String removeCharAt(String s, int pos) {      return s.substring(0, pos) + s.substring(pos + 1);   }}//字符串分隔替换这个例子说明了如何使用Java String类的replace 方法替换字符或子字符串。public class StringReplaceEmp{   public static void main(String args[]){      String str="Hello World";      System.out.println( str.replace( 'H','W' ) );      System.out.println( str.replaceFirst("He", "Wa") );      System.out.println( str.replaceAll("He", "Ha") );   }}//字符串反转下面的示例显示了如何通过命令行参数反转字符串。该程序使用StringBuffer(String string)方法输入字符串并反转缓冲区，然后将缓冲区使用toString() 转换成String。public class StringReverseExample{   public static void main(String[] args){      String string="abcdef";      String reverse = new StringBuffer(string).      reverse().toString();      System.out.println("String before reverse:      "+string);      System.out.println("String after reverse:      "+reverse);   }}//字符串搜索这个例子显示如何利用indexOf()方法在一个String对象中搜索一个词，如果找到那么返回字符串中一个字的位置索引。否则返回-1。 public class SearchStringEmp{   public static void main(String[] args) {      String strOrig = "Hello readers";      int intIndex = strOrig.indexOf("Hello");      if(intIndex == - 1){         System.out.println("Hello not found");      }else{         System.out.println("Found Hello at index "         + intIndex);      }   }}//字符串分割下面的例子将一个字符串转换成若干子字符串，在str的split(string)方法的帮助下，然后打印字符串。 public class JavaStringSplitEmp{   public static void main(String args[]){      String str = "jan-feb-march";      String[] temp;      String delimeter = "-";      temp = str.split(delimeter);      for(int i =0; i < temp.length ; i++){         System.out.println(temp[i]);         System.out.println("");         str = "jan.feb.march";         delimeter = "\.";         temp = str.split(delimeter);      }      for(int i =0; i < temp.length ; i++){         System.out.println(temp[i]);         System.out.println("");         temp = str.split(delimeter,2);         for(int j =0; j < temp.length ; j++){            System.out.println(temp[i]);         }      }   }}结果：janfebmarchjanjanjanfeb.marchfeb.marchfeb.march//字符串转换为大写 下面的示例将一个字符串转换为大写的使用String toUpperCase()方法的情况下完成。public class StringToUpperCaseEmp {   public static void main(String[] args) {      String str = "string abc touppercase ";      String strUpper = str.toUpperCase();      System.out.println("Original String: " + str);      System.out.println("String changed to upper case: "      + strUpper);   }}//字符串区域匹配下面的例子使用regionMatches()方法确定两个字符串区域匹配。public class StringRegionMatch{   public static void main(String[] args){      String first_str = "Welcome to Microsoft";      String second_str = "I work with Microsoft";      boolean match = first_str.      regionMatches(11, second_str, 12, 9);      System.out.println("first_str[11 -19] == "      + "second_str[12 - 21]:-"+ match);   }}结果：first_str[11 -19] == second_str[12 - 21]:-true //字符串连接下面的例子显示了通过使用“+”操作符和StringBuffer.append()方法拼接的性能。public class StringConcatenate{   public static void main(String[] args){      long startTime = System.currentTimeMillis();      for(int i=0;i<5000;i++){         String result = "This is"         + "testing the"         + "difference"+ "between"         + "String"+ "and"+ "StringBuffer";      }      long endTime = System.currentTimeMillis();      System.out.println("Time taken for string"       + "concatenation using + operator : "       + (endTime - startTime)+ " ms");      long startTime1 = System.currentTimeMillis();      for(int i=0;i<5000;i++){         StringBuffer result = new StringBuffer();         result.append("This is");         result.append("testing the");         result.append("difference");         result.append("between");         result.append("String");         result.append("and");         result.append("StringBuffer");      }      long endTime1 = System.currentTimeMillis();      System.out.println("Time taken for String concatenation"       + "using StringBuffer : "      + (endTime1 - startTime1)+ " ms");   }}//结果：Time taken for stringconcatenation using + operator : 0 msTime taken for String concatenationusing StringBuffer : 22 ms//如何缓冲字符串下面的例子字符串缓冲区，并通过使用emit()方法刷新它。 public class StringBuffer{   public static void main(String[] args) {      countTo_N_Improved();   }   private final static int MAX_LENGTH=30;   private static String buffer = "";   private static void emit(String nextChunk) {      if(buffer.length() + nextChunk.length() > MAX_LENGTH) {         System.out.println(buffer);         buffer = "";        }      buffer += nextChunk;   }   private static final int N=100;   private static void countTo_N_Improved() {      for (int count=2; count7lt;=N; count=count+2) {         emit(" " + count);      }   }}//运行结果：2 4 6 8 10 12 14 16 18 20 2224 26 28 30 32 34 36 38 40 4244 46 48 50 52 54 56 58 60 6264 66 68 70 72 74 76 78 80 82