StringBuilder 详解 (String系列之2)

本章介绍StringBuilder以及它的API的详细使用方法。

转载请注明出处：http://www.cnblogs.com/skywang12345/p/string02.html

StringBuilder 简介

StringBuilder 是一个可变的字符序列。它继承于AbstractStringBuilder，实现了CharSequence接口。
StringBuffer 也是继承于AbstractStringBuilder的子类；但是，StringBuilder和StringBuffer不同，前者是非线程安全的，后者是线程安全的。

StringBuilder 和 CharSequence之间的关系图如下：

StringBuilder函数列表

StringBuilder()StringBuilder(int capacity)StringBuilder(CharSequence seq)StringBuilder(String str)StringBuilder     append(float f)StringBuilder     append(double d)StringBuilder     append(boolean b)StringBuilder     append(int i)StringBuilder     append(long l)StringBuilder     append(char c)StringBuilder     append(char[] chars)StringBuilder     append(char[] str, int offset, int len)StringBuilder     append(String str)StringBuilder     append(Object obj)StringBuilder     append(StringBuffer sb)StringBuilder     append(CharSequence csq)StringBuilder     append(CharSequence csq, int start, int end)StringBuilder     appendCodePoint(int codePoint)int     capacity()char     charAt(int index)int     codePointAt(int index)int     codePointBefore(int index)int     codePointCount(int start, int end)StringBuilder     delete(int start, int end)StringBuilder     deleteCharAt(int index)void     ensureCapacity(int min)void     getChars(int start, int end, char[] dst, int dstStart)int     indexOf(String subString, int start)int     indexOf(String string)StringBuilder     insert(int offset, boolean b)StringBuilder     insert(int offset, int i)StringBuilder     insert(int offset, long l)StringBuilder     insert(int offset, float f)StringBuilder     insert(int offset, double d)StringBuilder     insert(int offset, char c)StringBuilder     insert(int offset, char[] ch)StringBuilder     insert(int offset, char[] str, int strOffset, int strLen)StringBuilder     insert(int offset, String str)StringBuilder     insert(int offset, Object obj)StringBuilder     insert(int offset, CharSequence s)StringBuilder     insert(int offset, CharSequence s, int start, int end)int     lastIndexOf(String string)int     lastIndexOf(String subString, int start)int     length()int     offsetByCodePoints(int index, int codePointOffset)StringBuilder     replace(int start, int end, String string)StringBuilder     reverse()void     setCharAt(int index, char ch)void     setLength(int length)CharSequence     subSequence(int start, int end)String     substring(int start)String     substring(int start, int end)String     toString()void     trimToSize()

 

AbstractStringBuilder 和 StringBuilder源码

AbstractStringBuilder源码(基于jdk1.7.40)

  1 package java.lang;  2   3 import sun.misc.FloatingDecimal;  4 import java.util.Arrays;  5   6 abstract class AbstractStringBuilder implements Appendable, CharSequence {  7     char[] value;  8   9     int count; 10  11     AbstractStringBuilder() { 12     } 13  14     AbstractStringBuilder(int capacity) { 15         value = new char[capacity]; 16     } 17  18     public int length() { 19         return count; 20     } 21  22     public int capacity() { 23         return value.length; 24     } 25  26     public void ensureCapacity(int minimumCapacity) { 27         if (minimumCapacity > 0) 28             ensureCapacityInternal(minimumCapacity); 29     } 30  31     private void ensureCapacityInternal(int minimumCapacity) { 32         // overflow-conscious code 33         if (minimumCapacity - value.length > 0) 34             expandCapacity(minimumCapacity); 35     } 36  37     void expandCapacity(int minimumCapacity) { 38         int newCapacity = value.length * 2 + 2; 39         if (newCapacity - minimumCapacity < 0) 40             newCapacity = minimumCapacity; 41         if (newCapacity < 0) { 42             if (minimumCapacity < 0) // overflow 43                 throw new OutOfMemoryError(); 44             newCapacity = Integer.MAX_VALUE; 45         } 46         value = Arrays.copyOf(value, newCapacity); 47     } 48  49     public void trimToSize() { 50         if (count < value.length) { 51             value = Arrays.copyOf(value, count); 52         } 53     } 54  55     public void setLength(int newLength) { 56         if (newLength < 0) 57             throw new StringIndexOutOfBoundsException(newLength); 58         ensureCapacityInternal(newLength); 59  60         if (count < newLength) { 61             for (; count < newLength; count++) 62                 value[count] = '\0'; 63         } else { 64             count = newLength; 65         } 66     } 67  68     public char charAt(int index) { 69         if ((index < 0) || (index >= count)) 70             throw new StringIndexOutOfBoundsException(index); 71         return value[index]; 72     } 73  74     public int codePointAt(int index) { 75         if ((index < 0) || (index >= count)) { 76             throw new StringIndexOutOfBoundsException(index); 77         } 78         return Character.codePointAt(value, index); 79     } 80  81     public int codePointBefore(int index) { 82         int i = index - 1; 83         if ((i < 0) || (i >= count)) { 84             throw new StringIndexOutOfBoundsException(index); 85         } 86         return Character.codePointBefore(value, index); 87     } 88  89     public int codePointCount(int beginIndex, int endIndex) { 90         if (beginIndex < 0 || endIndex > count || beginIndex > endIndex) { 91             throw new IndexOutOfBoundsException(); 92         } 93         return Character.codePointCountImpl(value, beginIndex, endIndex-beginIndex); 94     } 95  96     public int offsetByCodePoints(int index, int codePointOffset) { 97         if (index < 0 || index > count) { 98             throw new IndexOutOfBoundsException(); 99         }100         return Character.offsetByCodePointsImpl(value, 0, count,101                                                 index, codePointOffset);102     }103 104     public void getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin)105     {106         if (srcBegin < 0)107             throw new StringIndexOutOfBoundsException(srcBegin);108         if ((srcEnd < 0) || (srcEnd > count))109             throw new StringIndexOutOfBoundsException(srcEnd);110         if (srcBegin > srcEnd)111             throw new StringIndexOutOfBoundsException("srcBegin > srcEnd");112         System.arraycopy(value, srcBegin, dst, dstBegin, srcEnd - srcBegin);113     }114 115     public void setCharAt(int index, char ch) {116         if ((index < 0) || (index >= count))117             throw new StringIndexOutOfBoundsException(index);118         value[index] = ch;119     }120 121     public AbstractStringBuilder append(Object obj) {122         return append(String.valueOf(obj));123     }124 125     public AbstractStringBuilder append(String str) {126         if (str == null) str = "null";127         int len = str.length();128         ensureCapacityInternal(count + len);129         str.getChars(0, len, value, count);130         count += len;131         return this;132     }133 134     // Documentation in subclasses because of synchro difference135     public AbstractStringBuilder append(StringBuffer sb) {136         if (sb == null)137             return append("null");138         int len = sb.length();139         ensureCapacityInternal(count + len);140         sb.getChars(0, len, value, count);141         count += len;142         return this;143     }144 145     // Documentation in subclasses because of synchro difference146     public AbstractStringBuilder append(CharSequence s) {147         if (s == null)148             s = "null";149         if (s instanceof String)150             return this.append((String)s);151         if (s instanceof StringBuffer)152             return this.append((StringBuffer)s);153         return this.append(s, 0, s.length());154     }155 156     public AbstractStringBuilder append(CharSequence s, int start, int end) {157         if (s == null)158             s = "null";159         if ((start < 0) || (start > end) || (end > s.length()))160             throw new IndexOutOfBoundsException(161                 "start " + start + ", end " + end + ", s.length() "162                 + s.length());163         int len = end - start;164         ensureCapacityInternal(count + len);165         for (int i = start, j = count; i < end; i++, j++)166             value[j] = s.charAt(i);167         count += len;168         return this;169     }170 171     public AbstractStringBuilder append(char[] str) {172         int len = str.length;173         ensureCapacityInternal(count + len);174         System.arraycopy(str, 0, value, count, len);175         count += len;176         return this;177     }178 179     public AbstractStringBuilder append(char str[], int offset, int len) {180         if (len > 0)                // let arraycopy report AIOOBE for len < 0181             ensureCapacityInternal(count + len);182         System.arraycopy(str, offset, value, count, len);183         count += len;184         return this;185     }186 187     public AbstractStringBuilder append(boolean b) {188         if (b) {189             ensureCapacityInternal(count + 4);190             value[count++] = 't';191             value[count++] = 'r';192             value[count++] = 'u';193             value[count++] = 'e';194         } else {195             ensureCapacityInternal(count + 5);196             value[count++] = 'f';197             value[count++] = 'a';198             value[count++] = 'l';199             value[count++] = 's';200             value[count++] = 'e';201         }202         return this;203     }204 205     public AbstractStringBuilder append(char c) {206         ensureCapacityInternal(count + 1);207         value[count++] = c;208         return this;209     }210 211     public AbstractStringBuilder append(int i) {212         if (i == Integer.MIN_VALUE) {213             append("-2147483648");214             return this;215         }216         int appendedLength = (i < 0) ? Integer.stringSize(-i) + 1217                                      : Integer.stringSize(i);218         int spaceNeeded = count + appendedLength;219         ensureCapacityInternal(spaceNeeded);220         Integer.getChars(i, spaceNeeded, value);221         count = spaceNeeded;222         return this;223     }224 225     public AbstractStringBuilder append(long l) {226         if (l == Long.MIN_VALUE) {227             append("-9223372036854775808");228             return this;229         }230         int appendedLength = (l < 0) ? Long.stringSize(-l) + 1231                                      : Long.stringSize(l);232         int spaceNeeded = count + appendedLength;233         ensureCapacityInternal(spaceNeeded);234         Long.getChars(l, spaceNeeded, value);235         count = spaceNeeded;236         return this;237     }238 239     public AbstractStringBuilder append(float f) {240         new FloatingDecimal(f).appendTo(this);241         return this;242     }243 244     public AbstractStringBuilder append(double d) {245         new FloatingDecimal(d).appendTo(this);246         return this;247     }248 249     public AbstractStringBuilder delete(int start, int end) {250         if (start < 0)251             throw new StringIndexOutOfBoundsException(start);252         if (end > count)253             end = count;254         if (start > end)255             throw new StringIndexOutOfBoundsException();256         int len = end - start;257         if (len > 0) {258             System.arraycopy(value, start+len, value, start, count-end);259             count -= len;260         }261         return this;262     }263 264     public AbstractStringBuilder appendCodePoint(int codePoint) {265         final int count = this.count;266 267         if (Character.isBmpCodePoint(codePoint)) {268             ensureCapacityInternal(count + 1);269             value[count] = (char) codePoint;270             this.count = count + 1;271         } else if (Character.isValidCodePoint(codePoint)) {272             ensureCapacityInternal(count + 2);273             Character.toSurrogates(codePoint, value, count);274             this.count = count + 2;275         } else {276             throw new IllegalArgumentException();277         }278         return this;279     }280 281     public AbstractStringBuilder deleteCharAt(int index) {282         if ((index < 0) || (index >= count))283             throw new StringIndexOutOfBoundsException(index);284         System.arraycopy(value, index+1, value, index, count-index-1);285         count--;286         return this;287     }288 289     public AbstractStringBuilder replace(int start, int end, String str) {290         if (start < 0)291             throw new StringIndexOutOfBoundsException(start);292         if (start > count)293             throw new StringIndexOutOfBoundsException("start > length()");294         if (start > end)295             throw new StringIndexOutOfBoundsException("start > end");296 297         if (end > count)298             end = count;299         int len = str.length();300         int newCount = count + len - (end - start);301         ensureCapacityInternal(newCount);302 303         System.arraycopy(value, end, value, start + len, count - end);304         str.getChars(value, start);305         count = newCount;306         return this;307     }308 309     public String substring(int start) {310         return substring(start, count);311     }312 313     public CharSequence subSequence(int start, int end) {314         return substring(start, end);315     }316 317     public String substring(int start, int end) {318         if (start < 0)319             throw new StringIndexOutOfBoundsException(start);320         if (end > count)321             throw new StringIndexOutOfBoundsException(end);322         if (start > end)323             throw new StringIndexOutOfBoundsException(end - start);324         return new String(value, start, end - start);325     }326 327     public AbstractStringBuilder insert(int index, char[] str, int offset,328                                         int len)329     {330         if ((index < 0) || (index > length()))331             throw new StringIndexOutOfBoundsException(index);332         if ((offset < 0) || (len < 0) || (offset > str.length - len))333             throw new StringIndexOutOfBoundsException(334                 "offset " + offset + ", len " + len + ", str.length "335                 + str.length);336         ensureCapacityInternal(count + len);337         System.arraycopy(value, index, value, index + len, count - index);338         System.arraycopy(str, offset, value, index, len);339         count += len;340         return this;341     }342 343     public AbstractStringBuilder insert(int offset, Object obj) {344         return insert(offset, String.valueOf(obj));345     }346 347     public AbstractStringBuilder insert(int offset, String str) {348         if ((offset < 0) || (offset > length()))349             throw new StringIndexOutOfBoundsException(offset);350         if (str == null)351             str = "null";352         int len = str.length();353         ensureCapacityInternal(count + len);354         System.arraycopy(value, offset, value, offset + len, count - offset);355         str.getChars(value, offset);356         count += len;357         return this;358     }359 360     public AbstractStringBuilder insert(int offset, char[] str) {361         if ((offset < 0) || (offset > length()))362             throw new StringIndexOutOfBoundsException(offset);363         int len = str.length;364         ensureCapacityInternal(count + len);365         System.arraycopy(value, offset, value, offset + len, count - offset);366         System.arraycopy(str, 0, value, offset, len);367         count += len;368         return this;369     }370 371     public AbstractStringBuilder insert(int dstOffset, CharSequence s) {372         if (s == null)373             s = "null";374         if (s instanceof String)375             return this.insert(dstOffset, (String)s);376         return this.insert(dstOffset, s, 0, s.length());377     }378 379      public AbstractStringBuilder insert(int dstOffset, CharSequence s,380                                          int start, int end) {381         if (s == null)382             s = "null";383         if ((dstOffset < 0) || (dstOffset > this.length()))384             throw new IndexOutOfBoundsException("dstOffset "+dstOffset);385         if ((start < 0) || (end < 0) || (start > end) || (end > s.length()))386             throw new IndexOutOfBoundsException(387                 "start " + start + ", end " + end + ", s.length() "388                 + s.length());389         int len = end - start;390         ensureCapacityInternal(count + len);391         System.arraycopy(value, dstOffset, value, dstOffset + len,392                          count - dstOffset);393         for (int i=start; i<end; i++)394             value[dstOffset++] = s.charAt(i);395         count += len;396         return this;397     }398 399     public AbstractStringBuilder insert(int offset, boolean b) {400         return insert(offset, String.valueOf(b));401     }402 403     public AbstractStringBuilder insert(int offset, char c) {404         ensureCapacityInternal(count + 1);405         System.arraycopy(value, offset, value, offset + 1, count - offset);406         value[offset] = c;407         count += 1;408         return this;409     }410 411     public AbstractStringBuilder insert(int offset, int i) {412         return insert(offset, String.valueOf(i));413     }414 415     public AbstractStringBuilder insert(int offset, long l) {416         return insert(offset, String.valueOf(l));417     }418 419     public AbstractStringBuilder insert(int offset, float f) {420         return insert(offset, String.valueOf(f));421     }422 423     public AbstractStringBuilder insert(int offset, double d) {424         return insert(offset, String.valueOf(d));425     }426 427     public int indexOf(String str) {428         return indexOf(str, 0);429     }430 431     public int indexOf(String str, int fromIndex) {432         return String.indexOf(value, 0, count,433                               str.toCharArray(), 0, str.length(), fromIndex);434     }435 436     public int lastIndexOf(String str) {437         return lastIndexOf(str, count);438     }439 440     public int lastIndexOf(String str, int fromIndex) {441         return String.lastIndexOf(value, 0, count,442                               str.toCharArray(), 0, str.length(), fromIndex);443     }444 445     public AbstractStringBuilder reverse() {446         boolean hasSurrogate = false;447         int n = count - 1;448         for (int j = (n-1) >> 1; j >= 0; --j) {449             char temp = value[j];450             char temp2 = value[n - j];451             if (!hasSurrogate) {452                 hasSurrogate = (temp >= Character.MIN_SURROGATE && temp <= Character.MAX_SURROGATE)453                     || (temp2 >= Character.MIN_SURROGATE && temp2 <= Character.MAX_SURROGATE);454             }455             value[j] = temp2;456             value[n - j] = temp;457         }458         if (hasSurrogate) {459             // Reverse back all valid surrogate pairs460             for (int i = 0; i < count - 1; i++) {461                 char c2 = value[i];462                 if (Character.isLowSurrogate(c2)) {463                     char c1 = value[i + 1];464                     if (Character.isHighSurrogate(c1)) {465                         value[i++] = c1;466                         value[i] = c2;467                     }468                 }469             }470         }471         return this;472     }473 474     public abstract String toString();475 476     final char[] getValue() {477         return value;478     }479 }

StringBuilder源码(基于jdk1.7.40)

  1 package java.lang;  2   3 public final class StringBuilder  4     extends AbstractStringBuilder  5     implements java.io.Serializable, CharSequence {  6   7     static final long serialVersionUID = 4383685877147921099L;  8   9     // 构造函数。默认的字符数组大小是16。 10     public StringBuilder() { 11         super(16); 12     } 13  14     // 构造函数。指定StringBuilder的字符数组大小是capacity。 15     public StringBuilder(int capacity) { 16         super(capacity); 17     } 18  19     // 构造函数。指定字符数组大小=str长度+15，且将str的值赋值到当前字符数组中。 20     public StringBuilder(String str) { 21         super(str.length() + 16); 22         append(str); 23     } 24  25     // 构造函数。指定字符数组大小=seq长度+15，且将seq的值赋值到当前字符数组中。 26     public StringBuilder(CharSequence seq) { 27         this(seq.length() + 16); 28         append(seq); 29     } 30  31     // 追加“对象obj对应的字符串”。String.valueOf(obj)实际上是调用obj.toString() 32     public StringBuilder append(Object obj) { 33         return append(String.valueOf(obj)); 34     } 35  36     // 追加“str”。 37     public StringBuilder append(String str) { 38         super.append(str); 39         return this; 40     } 41  42     // 追加“sb的内容”。 43     private StringBuilder append(StringBuilder sb) { 44         if (sb == null) 45             return append("null"); 46         int len = sb.length(); 47         int newcount = count + len; 48         if (newcount > value.length) 49             expandCapacity(newcount); 50         sb.getChars(0, len, value, count); 51         count = newcount; 52         return this; 53     } 54  55     // 追加“sb的内容”。 56     public StringBuilder append(StringBuffer sb) { 57         super.append(sb); 58         return this; 59     } 60  61     // 追加“s的内容”。 62     public StringBuilder append(CharSequence s) { 63         if (s == null) 64             s = "null"; 65         if (s instanceof String) 66             return this.append((String)s); 67         if (s instanceof StringBuffer) 68             return this.append((StringBuffer)s); 69         if (s instanceof StringBuilder) 70             return this.append((StringBuilder)s); 71         return this.append(s, 0, s.length()); 72     } 73  74     // 追加“s从start(包括)到end(不包括)的内容”。 75     public StringBuilder append(CharSequence s, int start, int end) { 76         super.append(s, start, end); 77         return this; 78     } 79  80     // 追加“str字符数组对应的字符串” 81     public StringBuilder append(char[] str) { 82         super.append(str); 83         return this; 84     } 85  86     // 追加“str从offset开始的内容，内容长度是len” 87     public StringBuilder append(char[] str, int offset, int len) { 88         super.append(str, offset, len); 89         return this; 90     } 91  92     // 追加“b对应的字符串” 93     public StringBuilder append(boolean b) { 94         super.append(b); 95         return this; 96     } 97  98     // 追加“c” 99     public StringBuilder append(char c) {100         super.append(c);101         return this;102     }103 104     // 追加“i”105     public StringBuilder append(int i) {106         super.append(i);107         return this;108     }109 110     // 追加“lng”111     public StringBuilder append(long lng) {112         super.append(lng);113         return this;114     }115 116     // 追加“f”117     public StringBuilder append(float f) {118         super.append(f);119         return this;120     }121 122     // 追加“d”123     public StringBuilder append(double d) {124         super.append(d);125         return this;126     }127 128     // 追加“codePoint”129     public StringBuilder appendCodePoint(int codePoint) {130         super.appendCodePoint(codePoint);131         return this;132     }133 134     // 删除“从start(包括)到end的内容”135     public StringBuilder delete(int start, int end) {136         super.delete(start, end);137         return this;138     }139 140     // 删除“位置index的内容”141     public StringBuilder deleteCharAt(int index) {142         super.deleteCharAt(index);143         return this;144     }145 146     // “用str替换StringBuilder中从start(包括)到end(不包括)的内容”147     public StringBuilder replace(int start, int end, String str) {148         super.replace(start, end, str);149         return this;150     }151 152     // “在StringBuilder的位置index处插入‘str中从offset开始的内容’，插入内容长度是len”153     public StringBuilder insert(int index, char[] str, int offset,154                                 int len)155     {156         super.insert(index, str, offset, len);157         return this;158     }159 160     // “在StringBuilder的位置offset处插入obj对应的字符串”161     public StringBuilder insert(int offset, Object obj) {162         return insert(offset, String.valueOf(obj));163     }164 165     // “在StringBuilder的位置offset处插入str”166     public StringBuilder insert(int offset, String str) {167         super.insert(offset, str);168         return this;169     }170 171     // “在StringBuilder的位置offset处插入str”172     public StringBuilder insert(int offset, char[] str) {173         super.insert(offset, str);174         return this;175     }176 177     // “在StringBuilder的位置dstOffset处插入s”178     public StringBuilder insert(int dstOffset, CharSequence s) {179         if (s == null)180             s = "null";181         if (s instanceof String)182             return this.insert(dstOffset, (String)s);183         return this.insert(dstOffset, s, 0, s.length());184     }185 186     // “在StringBuilder的位置dstOffset处插入's中从start到end的内容'”187     public StringBuilder insert(int dstOffset, CharSequence s,188                                 int start, int end)189     {190         super.insert(dstOffset, s, start, end);191         return this;192     }193 194     // “在StringBuilder的位置Offset处插入b”195     public StringBuilder insert(int offset, boolean b) {196         super.insert(offset, b);197         return this;198     }199 200     // “在StringBuilder的位置Offset处插入c”201     public StringBuilder insert(int offset, char c) {202         super.insert(offset, c);203         return this;204     }205 206     // “在StringBuilder的位置Offset处插入i”207     public StringBuilder insert(int offset, int i) {208         return insert(offset, String.valueOf(i));209     }210 211     // “在StringBuilder的位置Offset处插入l”212     public StringBuilder insert(int offset, long l) {213         return insert(offset, String.valueOf(l));214     }215 216     // “在StringBuilder的位置Offset处插入f”217     public StringBuilder insert(int offset, float f) {218         return insert(offset, String.valueOf(f));219     }220 221     // “在StringBuilder的位置Offset处插入d”222     public StringBuilder insert(int offset, double d) {223         return insert(offset, String.valueOf(d));224     }225 226     // 返回“str”在StringBuilder的位置227     public int indexOf(String str) {228         return indexOf(str, 0);229     }230 231     // 从fromIndex开始查找，返回“str”在StringBuilder的位置232     public int indexOf(String str, int fromIndex) {233         return String.indexOf(value, 0, count,234                               str.toCharArray(), 0, str.length(), fromIndex);235     }236 237     // 从后向前查找，返回“str”在StringBuilder的位置238     public int lastIndexOf(String str) {239         return lastIndexOf(str, count);240     }241 242     // 从fromIndex开始，从后向前查找，返回“str”在StringBuilder的位置243     public int lastIndexOf(String str, int fromIndex) {244         return String.lastIndexOf(value, 0, count,245                               str.toCharArray(), 0, str.length(), fromIndex);246     }247 248     // 反转StringBuilder249     public StringBuilder reverse() {250         super.reverse();251         return this;252     }253 254     public String toString() {255         // Create a copy, don't share the array256         return new String(value, 0, count);257     }258 259     // 序列化对应的写入函数260     private void writeObject(java.io.ObjectOutputStream s)261         throws java.io.IOException {262         s.defaultWriteObject();263         s.writeInt(count);264         s.writeObject(value);265     }266 267     // 序列化对应的读取函数268     private void readObject(java.io.ObjectInputStream s)269         throws java.io.IOException, ClassNotFoundException {270         s.defaultReadObject();271         count = s.readInt();272         value = (char[]) s.readObject();273     }274 }

 

1. StringBuilder 中插入(insert)相关的API

源码如下(StringBuilderInsertTest.java):

 1 /** 2  * StringBuilder 的insert()示例 3  * 4  * @author skywang 5  */ 6 import java.util.HashMap; 7  8 public class StringBuilderInsertTest { 9 10     public static void main(String[] args) {11         testInsertAPIs() ;12     }13 14     /**15      * StringBuilder 的insert()示例16      */17     private static void testInsertAPIs() {18 19         System.out.println("-------------------------------- testInsertAPIs -------------------------------");20 21         StringBuilder sbuilder = new StringBuilder();22 23         // 在位置0处插入字符数组24         sbuilder.insert(0, new char[]{'a','b','c','d','e'});25         // 在位置0处插入字符数组。0表示字符数组起始位置，3表示长度26         sbuilder.insert(0, new char[]{'A','B','C','D','E'}, 0, 3);27         // 在位置0处插入float28         sbuilder.insert(0, 1.414f);29         // 在位置0处插入double30         sbuilder.insert(0, 3.14159d);31         // 在位置0处插入boolean32         sbuilder.insert(0, true);33         // 在位置0处插入char34         sbuilder.insert(0, '\n');35         // 在位置0处插入int36         sbuilder.insert(0, 100);37         // 在位置0处插入long38         sbuilder.insert(0, 12345L);39         // 在位置0处插入StringBuilder对象40         sbuilder.insert(0, new StringBuilder("StringBuilder"));41         // 在位置0处插入StringBuilder对象。6表示被在位置0处插入对象的起始位置(包括)，13是结束位置(不包括)42         sbuilder.insert(0, new StringBuilder("STRINGBUILDER"), 6, 13);43         // 在位置0处插入StringBuffer对象。44         sbuilder.insert(0, new StringBuffer("StringBuffer"));45         // 在位置0处插入StringBuffer对象。6表示被在位置0处插入对象的起始位置(包括)，12是结束位置(不包括)46         sbuilder.insert(0, new StringBuffer("STRINGBUFFER"), 6, 12);47         // 在位置0处插入String对象。48         sbuilder.insert(0, "String");49         // 在位置0处插入String对象。1表示被在位置0处插入对象的起始位置(包括)，6是结束位置(不包括)50         sbuilder.insert(0, "0123456789", 1, 6);51         sbuilder.insert(0, '\n');52 53         // 在位置0处插入Object对象。此处以HashMap为例54         HashMap map = new HashMap();55         map.put("1", "one");56         map.put("2", "two");57         map.put("3", "three");58         sbuilder.insert(0, map);59 60         System.out.printf("%s\n\n", sbuilder);61     }62 }

运行结果：

-------------------------------- testInsertAPIs -------------------------------{3=three, 2=two, 1=one}12345StringBUFFERStringBufferBUILDERStringBuilder12345100true3.141591.414ABCabcde

 

2. StringBuilder 中追加(append)相关的API

源码如下(StringBuilderAppendTest.java):

 1 /** 2  * StringBuilder 的append()示例 3  * 4  * @author skywang 5  */ 6 import java.util.HashMap; 7  8 public class StringBuilderAppendTest { 9 10     public static void main(String[] args) {11         testAppendAPIs() ;12     }13 14     /**15      * StringBuilder 的append()示例16      */17     private static void testAppendAPIs() {18 19         System.out.println("-------------------------------- testAppendAPIs -------------------------------");20 21         StringBuilder sbuilder = new StringBuilder();22 23         // 追加字符数组24         sbuilder.append(new char[]{'a','b','c','d','e'});25         // 追加字符数组。0表示字符数组起始位置，3表示长度26         sbuilder.append(new char[]{'A','B','C','D','E'}, 0, 3);27         // 追加float28         sbuilder.append(1.414f);29         // 追加double30         sbuilder.append(3.14159d);31         // 追加boolean32         sbuilder.append(true);33         // 追加char34         sbuilder.append('\n');35         // 追加int36         sbuilder.append(100);37         // 追加long38         sbuilder.append(12345L);39         // 追加StringBuilder对象40         sbuilder.append(new StringBuilder("StringBuilder"));41         // 追加StringBuilder对象。6表示被追加对象的起始位置(包括)，13是结束位置(不包括)42         sbuilder.append(new StringBuilder("STRINGBUILDER"), 6, 13);43         // 追加StringBuffer对象。44         sbuilder.append(new StringBuffer("StringBuffer"));45         // 追加StringBuffer对象。6表示被追加对象的起始位置(包括)，12是结束位置(不包括)46         sbuilder.append(new StringBuffer("STRINGBUFFER"), 6, 12);47         // 追加String对象。48         sbuilder.append("String");49         // 追加String对象。1表示被追加对象的起始位置(包括)，6是结束位置(不包括)50         sbuilder.append("0123456789", 1, 6);51         sbuilder.append('\n');52 53         // 追加Object对象。此处以HashMap为例54         HashMap map = new HashMap();55         map.put("1", "one");56         map.put("2", "two");57         map.put("3", "three");58         sbuilder.append(map);59         sbuilder.append('\n');60 61         // 追加unicode编码62         sbuilder.appendCodePoint(0x5b57);    // 0x5b57是“字”的unicode编码63         sbuilder.appendCodePoint(0x7b26);    // 0x7b26是“符”的unicode编码64         sbuilder.appendCodePoint(0x7f16);    // 0x7f16是“编”的unicode编码65         sbuilder.appendCodePoint(0x7801);    // 0x7801是“码”的unicode编码66 67         System.out.printf("%s\n\n", sbuilder);68     }69 }

运行结果：

-------------------------------- testAppendAPIs -------------------------------abcdeABC1.4143.14159true10012345StringBuilderBUILDERStringBufferBUFFERString12345{3=three, 2=two, 1=one}字符编码

 

3. StringBuilder 中替换(replace)相关的API

源码如下(StringBuilderReplaceTest.java):

 1 /** 2  * StringBuilder 的replace()示例 3  * 4  * @author skywang 5  */ 6 import java.util.HashMap; 7  8 public class StringBuilderReplaceTest { 9 10     public static void main(String[] args) {11         testReplaceAPIs() ;12     }13 14     /**15      * StringBuilder 的replace()示例16      */17     private static void testReplaceAPIs() {18 19         System.out.println("-------------------------------- testReplaceAPIs ------------------------------");20 21         StringBuilder sbuilder;22 23         sbuilder = new StringBuilder("0123456789");24         sbuilder.replace(0, 3, "ABCDE");25         System.out.printf("sbuilder=%s\n", sbuilder);26 27         sbuilder = new StringBuilder("0123456789");28         sbuilder.reverse();29         System.out.printf("sbuilder=%s\n", sbuilder);30 31         sbuilder = new StringBuilder("0123456789");32         sbuilder.setCharAt(0, 'M');33         System.out.printf("sbuilder=%s\n", sbuilder);34 35         System.out.println();36     }37 }

运行结果：

-------------------------------- testReplaceAPIs ------------------------------sbuilder=ABCDE3456789sbuilder=9876543210sbuilder=M123456789

 

4. StringBuilder 中删除(delete)相关的API

源码如下(StringBuilderDeleteTest.java):

 1 /** 2  * StringBuilder 的delete()示例 3  * 4  * @author skywang 5  */ 6 import java.util.HashMap; 7  8 public class StringBuilderDeleteTest { 9 10     public static void main(String[] args) {11         testDeleteAPIs() ;12     }13 14     /**15      * StringBuilder 的delete()示例16      */17     private static void testDeleteAPIs() {18 19         System.out.println("-------------------------------- testDeleteAPIs -------------------------------");20 21         StringBuilder sbuilder = new StringBuilder("0123456789");22         23         // 删除位置0的字符，剩余字符是“123456789”。24         sbuilder.deleteCharAt(0);25         // 删除位置3(包括)到位置6(不包括)之间的字符，剩余字符是“123789”。26         sbuilder.delete(3,6);27 28         // 获取sb中从位置1开始的字符串29         String str1 = sbuilder.substring(1);30         // 获取sb中从位置3(包括)到位置5(不包括)之间的字符串31         String str2 = sbuilder.substring(3, 5);32         // 获取sb中从位置3(包括)到位置5(不包括)之间的字符串，获取的对象是CharSequence对象，此处转型为String33         String str3 = (String)sbuilder.subSequence(3, 5);34 35         System.out.printf("sbuilder=%s\nstr1=%s\nstr2=%s\nstr3=%s\n", 36                 sbuilder, str1, str2, str3);37     }38 }

运行结果：

-------------------------------- testDeleteAPIs -------------------------------sbuilder=123789str1=23789str2=78str3=78

 

5. StringBuilder 中index相关的API

源码如下(StringBuilderIndexTest.java):

 1 /** 2  * StringBuilder 中index相关API演示 3  * 4  * @author skywang 5  */ 6 import java.util.HashMap; 7  8 public class StringBuilderIndexTest { 9 10     public static void main(String[] args) {11         testIndexAPIs() ;12     }13 14     /**15      * StringBuilder 中index相关API演示16      */17     private static void testIndexAPIs() {18         System.out.println("-------------------------------- testIndexAPIs --------------------------------");19 20         StringBuilder sbuilder = new StringBuilder("abcAbcABCabCaBcAbCaBCabc");21         System.out.printf("sbuilder=%s\n", sbuilder);22 23         // 1. 从前往后，找出"bc"第一次出现的位置24         System.out.printf("%-30s = %d\n", "sbuilder.indexOf(\"bc\")", sbuilder.indexOf("bc"));25 26         // 2. 从位置5开始，从前往后，找出"bc"第一次出现的位置27         System.out.printf("%-30s = %d\n", "sbuilder.indexOf(\"bc\", 5)", sbuilder.indexOf("bc", 5));28 29         // 3. 从后往前，找出"bc"第一次出现的位置30         System.out.printf("%-30s = %d\n", "sbuilder.lastIndexOf(\"bc\")", sbuilder.lastIndexOf("bc"));31 32         // 4. 从位置4开始，从后往前，找出"bc"第一次出现的位置33         System.out.printf("%-30s = %d\n", "sbuilder.lastIndexOf(\"bc\", 4)", sbuilder.lastIndexOf("bc", 4));34 35         System.out.println();36     }37 }

运行结果：

-------------------------------- testIndexAPIs --------------------------------sbuilder=abcAbcABCabCaBcAbCaBCabcsbuilder.indexOf("bc")         = 1sbuilder.indexOf("bc", 5)      = 22sbuilder.lastIndexOf("bc")     = 22sbuilder.lastIndexOf("bc", 4)  = 4

 

6. StringBuilder 剩余的API

源码如下(StringBuilderOtherTest.java):

 1 /** 2  * StringBuilder 的其它API示例 3  * 4  * @author skywang 5  */ 6 import java.util.HashMap; 7  8 public class StringBuilderOtherTest { 9 10     public static void main(String[] args) {11         testOtherAPIs() ;12     }13 14     /**15      * StringBuilder 的其它API示例16      */17     private static void testOtherAPIs() {18 19         System.out.println("-------------------------------- testOtherAPIs --------------------------------");20 21         StringBuilder sbuilder = new StringBuilder("0123456789");22 23         int cap = sbuilder.capacity();24         System.out.printf("cap=%d\n", cap);25 26         char c = sbuilder.charAt(6);27         System.out.printf("c=%c\n", c);28 29         char[] carr = new char[4];30         sbuilder.getChars(3, 7, carr, 0);31         for (int i=0; i<carr.length; i++)32             System.out.printf("carr[%d]=%c ", i, carr[i]);33         System.out.println();34 35         System.out.println();36     }37 }

运行结果：

-------------------------------- testOtherAPIs --------------------------------cap=26c=6carr[0]=3 carr[1]=4 carr[2]=5 carr[3]=6 

 

7. StringBuilder 完整示例

下面的示例是整合上面的几个示例的完整的StringBuilder演示程序，源码如下(StringBuilderTest.java):

  1 /**  2  * StringBuilder 演示程序  3  *  4  * @author skywang  5  */  6 import java.util.HashMap;  7   8 public class StringBuilderTest {  9  10     public static void main(String[] args) { 11         testOtherAPIs() ; 12         testIndexAPIs() ; 13         testInsertAPIs() ; 14         testAppendAPIs() ; 15         testReplaceAPIs() ; 16         testDeleteAPIs() ; 17     } 18  19     /** 20      * StringBuilder 的其它API示例 21      */ 22     private static void testOtherAPIs() { 23  24         System.out.println("-------------------------------- testOtherAPIs --------------------------------"); 25  26         StringBuilder sbuilder = new StringBuilder("0123456789"); 27  28         int cap = sbuilder.capacity(); 29         System.out.printf("cap=%d\n", cap); 30  31         char c = sbuilder.charAt(6); 32         System.out.printf("c=%c\n", c); 33  34         char[] carr = new char[4]; 35         sbuilder.getChars(3, 7, carr, 0); 36         for (int i=0; i<carr.length; i++) 37             System.out.printf("carr[%d]=%c ", i, carr[i]); 38         System.out.println(); 39  40         System.out.println(); 41     } 42  43     /** 44      * StringBuilder 中index相关API演示 45      */ 46     private static void testIndexAPIs() { 47         System.out.println("-------------------------------- testIndexAPIs --------------------------------"); 48  49         StringBuilder sbuilder = new StringBuilder("abcAbcABCabCaBcAbCaBCabc"); 50         System.out.printf("sbuilder=%s\n", sbuilder); 51  52         // 1. 从前往后，找出"bc"第一次出现的位置 53         System.out.printf("%-30s = %d\n", "sbuilder.indexOf(\"bc\")", sbuilder.indexOf("bc")); 54  55         // 2. 从位置5开始，从前往后，找出"bc"第一次出现的位置 56         System.out.printf("%-30s = %d\n", "sbuilder.indexOf(\"bc\", 5)", sbuilder.indexOf("bc", 5)); 57  58         // 3. 从后往前，找出"bc"第一次出现的位置 59         System.out.printf("%-30s = %d\n", "sbuilder.lastIndexOf(\"bc\")", sbuilder.lastIndexOf("bc")); 60  61         // 4. 从位置4开始，从后往前，找出"bc"第一次出现的位置 62         System.out.printf("%-30s = %d\n", "sbuilder.lastIndexOf(\"bc\", 4)", sbuilder.lastIndexOf("bc", 4)); 63  64         System.out.println(); 65     } 66  67     /** 68      * StringBuilder 的replace()示例 69      */ 70     private static void testReplaceAPIs() { 71  72         System.out.println("-------------------------------- testReplaceAPIs ------------------------------"); 73  74         StringBuilder sbuilder; 75  76         sbuilder = new StringBuilder("0123456789"); 77         sbuilder.replace(0, 3, "ABCDE"); 78         System.out.printf("sbuilder=%s\n", sbuilder); 79  80         sbuilder = new StringBuilder("0123456789"); 81         sbuilder.reverse(); 82         System.out.printf("sbuilder=%s\n", sbuilder); 83  84         sbuilder = new StringBuilder("0123456789"); 85         sbuilder.setCharAt(0, 'M'); 86         System.out.printf("sbuilder=%s\n", sbuilder); 87  88         System.out.println(); 89     } 90  91     /** 92      * StringBuilder 的delete()示例 93      */ 94     private static void testDeleteAPIs() { 95  96         System.out.println("-------------------------------- testDeleteAPIs -------------------------------"); 97  98         StringBuilder sbuilder = new StringBuilder("0123456789"); 99         100         // 删除位置0的字符，剩余字符是“123456789”。101         sbuilder.deleteCharAt(0);102         // 删除位置3(包括)到位置6(不包括)之间的字符，剩余字符是“123789”。103         sbuilder.delete(3,6);104 105         // 获取sb中从位置1开始的字符串106         String str1 = sbuilder.substring(1);107         // 获取sb中从位置3(包括)到位置5(不包括)之间的字符串108         String str2 = sbuilder.substring(3, 5);109         // 获取sb中从位置3(包括)到位置5(不包括)之间的字符串，获取的对象是CharSequence对象，此处转型为String110         String str3 = (String)sbuilder.subSequence(3, 5);111 112         System.out.printf("sbuilder=%s\nstr1=%s\nstr2=%s\nstr3=%s\n", 113                 sbuilder, str1, str2, str3);114     }115 116     /**117      * StringBuilder 的insert()示例118      */119     private static void testInsertAPIs() {120 121         System.out.println("-------------------------------- testInsertAPIs -------------------------------");122 123         StringBuilder sbuilder = new StringBuilder();124 125         // 在位置0处插入字符数组126         sbuilder.insert(0, new char[]{'a','b','c','d','e'});127         // 在位置0处插入字符数组。0表示字符数组起始位置，3表示长度128         sbuilder.insert(0, new char[]{'A','B','C','D','E'}, 0, 3);129         // 在位置0处插入float130         sbuilder.insert(0, 1.414f);131         // 在位置0处插入double132         sbuilder.insert(0, 3.14159d);133         // 在位置0处插入boolean134         sbuilder.insert(0, true);135         // 在位置0处插入char136         sbuilder.insert(0, '\n');137         // 在位置0处插入int138         sbuilder.insert(0, 100);139         // 在位置0处插入long140         sbuilder.insert(0, 12345L);141         // 在位置0处插入StringBuilder对象142         sbuilder.insert(0, new StringBuilder("StringBuilder"));143         // 在位置0处插入StringBuilder对象。6表示被在位置0处插入对象的起始位置(包括)，13是结束位置(不包括)144         sbuilder.insert(0, new StringBuilder("STRINGBUILDER"), 6, 13);145         // 在位置0处插入StringBuffer对象。146         sbuilder.insert(0, new StringBuffer("StringBuffer"));147         // 在位置0处插入StringBuffer对象。6表示被在位置0处插入对象的起始位置(包括)，12是结束位置(不包括)148         sbuilder.insert(0, new StringBuffer("STRINGBUFFER"), 6, 12);149         // 在位置0处插入String对象。150         sbuilder.insert(0, "String");151         // 在位置0处插入String对象。1表示被在位置0处插入对象的起始位置(包括)，6是结束位置(不包括)152         sbuilder.insert(0, "0123456789", 1, 6);153         sbuilder.insert(0, '\n');154 155         // 在位置0处插入Object对象。此处以HashMap为例156         HashMap map = new HashMap();157         map.put("1", "one");158         map.put("2", "two");159         map.put("3", "three");160         sbuilder.insert(0, map);161 162         System.out.printf("%s\n\n", sbuilder);163     }164 165     /**166      * StringBuilder 的append()示例167      */168     private static void testAppendAPIs() {169 170         System.out.println("-------------------------------- testAppendAPIs -------------------------------");171 172         StringBuilder sbuilder = new StringBuilder();173 174         // 追加字符数组175         sbuilder.append(new char[]{'a','b','c','d','e'});176         // 追加字符数组。0表示字符数组起始位置，3表示长度177         sbuilder.append(new char[]{'A','B','C','D','E'}, 0, 3);178         // 追加float179         sbuilder.append(1.414f);180         // 追加double181         sbuilder.append(3.14159d);182         // 追加boolean183         sbuilder.append(true);184         // 追加char185         sbuilder.append('\n');186         // 追加int187         sbuilder.append(100);188         // 追加long189         sbuilder.append(12345L);190         // 追加StringBuilder对象191         sbuilder.append(new StringBuilder("StringBuilder"));192         // 追加StringBuilder对象。6表示被追加对象的起始位置(包括)，13是结束位置(不包括)193         sbuilder.append(new StringBuilder("STRINGBUILDER"), 6, 13);194         // 追加StringBuffer对象。195         sbuilder.append(new StringBuffer("StringBuffer"));196         // 追加StringBuffer对象。6表示被追加对象的起始位置(包括)，12是结束位置(不包括)197         sbuilder.append(new StringBuffer("STRINGBUFFER"), 6, 12);198         // 追加String对象。199         sbuilder.append("String");200         // 追加String对象。1表示被追加对象的起始位置(包括)，6是结束位置(不包括)201         sbuilder.append("0123456789", 1, 6);202         sbuilder.append('\n');203 204         // 追加Object对象。此处以HashMap为例205         HashMap map = new HashMap();206         map.put("1", "one");207         map.put("2", "two");208         map.put("3", "three");209         sbuilder.append(map);210         sbuilder.append('\n');211 212         // 追加unicode编码213         sbuilder.appendCodePoint(0x5b57);    // 0x5b57是“字”的unicode编码214         sbuilder.appendCodePoint(0x7b26);    // 0x7b26是“符”的unicode编码215         sbuilder.appendCodePoint(0x7f16);    // 0x7f16是“编”的unicode编码216         sbuilder.appendCodePoint(0x7801);    // 0x7801是“码”的unicode编码217 218         System.out.printf("%s\n\n", sbuilder);219     }220 }