StringBuilder 詳解 (String系列之2)

本文轉載自查看原文 2013-11-08 08:33 47196 Java/ StringBuilder

本章介紹StringBuilder以及它的API的詳細使用方法。

轉載請注明出處：http://www.cnblogs.com/skywang12345/p/string02.html

StringBuilder 簡介

StringBuilder 是一個可變的字符序列。它繼承於AbstractStringBuilder，實現了CharSequence接口。
StringBuffer 也是繼承於AbstractStringBuilder的子類；但是，StringBuilder和StringBuffer不同，前者是非線程安全的，后者是線程安全的。

StringBuilder 和 CharSequence之間的關系圖如下：

StringBuilder函數列表

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源碼

AbstractStringBuilder源碼(基於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 difference
135     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 difference
146     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 < 0
181             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) + 1
217                                      : 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) + 1
231                                      : 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 pairs
460             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 }

View Code

StringBuilder源碼(基於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     // 構造函數。默認的字符數組大小是16。
 10     public StringBuilder() {
 11         super(16);
 12     }
 13 
 14     // 構造函數。指定StringBuilder的字符數組大小是capacity。
 15     public StringBuilder(int capacity) {
 16         super(capacity);
 17     }
 18 
 19     // 構造函數。指定字符數組大小=str長度+15，且將str的值賦值到當前字符數組中。
 20     public StringBuilder(String str) {
 21         super(str.length() + 16);
 22         append(str);
 23     }
 24 
 25     // 構造函數。指定字符數組大小=seq長度+15，且將seq的值賦值到當前字符數組中。
 26     public StringBuilder(CharSequence seq) {
 27         this(seq.length() + 16);
 28         append(seq);
 29     }
 30 
 31     // 追加“對象obj對應的字符串”。String.valueOf(obj)實際上是調用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的內容”。
 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的內容”。
 56     public StringBuilder append(StringBuffer sb) {
 57         super.append(sb);
 58         return this;
 59     }
 60 
 61     // 追加“s的內容”。
 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從start(包括)到end(不包括)的內容”。
 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字符數組對應的字符串”
 81     public StringBuilder append(char[] str) {
 82         super.append(str);
 83         return this;
 84     }
 85 
 86     // 追加“str從offset開始的內容，內容長度是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對應的字符串”
 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     // 刪除“從start(包括)到end的內容”
135     public StringBuilder delete(int start, int end) {
136         super.delete(start, end);
137         return this;
138     }
139 
140     // 刪除“位置index的內容”
141     public StringBuilder deleteCharAt(int index) {
142         super.deleteCharAt(index);
143         return this;
144     }
145 
146     // “用str替換StringBuilder中從start(包括)到end(不包括)的內容”
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處插入‘str中從offset開始的內容’，插入內容長度是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處插入obj對應的字符串”
161     public StringBuilder insert(int offset, Object obj) {
162         return insert(offset, String.valueOf(obj));
163     }
164 
165     // “在StringBuilder的位置offset處插入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處插入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處插入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處插入's中從start到end的內容'”
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處插入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處插入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處插入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處插入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處插入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處插入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     // 從fromIndex開始查找，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     // 從后向前查找，返回“str”在StringBuilder的位置
238     public int lastIndexOf(String str) {
239         return lastIndexOf(str, count);
240     }
241 
242     // 從fromIndex開始，從后向前查找，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     // 反轉StringBuilder
249     public StringBuilder reverse() {
250         super.reverse();
251         return this;
252     }
253 
254     public String toString() {
255         // Create a copy, don't share the array
256         return new String(value, 0, count);
257     }
258 
259     // 序列化對應的寫入函數
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     // 序列化對應的讀取函數
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 }

View Code

1. StringBuilder 中插入(insert)相關的API

源碼如下(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處插入字符數組
24         sbuilder.insert(0, new char[]{'a','b','c','d','e'});
25         // 在位置0處插入字符數組。0表示字符數組起始位置，3表示長度
26         sbuilder.insert(0, new char[]{'A','B','C','D','E'}, 0, 3);
27         // 在位置0處插入float
28         sbuilder.insert(0, 1.414f);
29         // 在位置0處插入double
30         sbuilder.insert(0, 3.14159d);
31         // 在位置0處插入boolean
32         sbuilder.insert(0, true);
33         // 在位置0處插入char
34         sbuilder.insert(0, '\n');
35         // 在位置0處插入int
36         sbuilder.insert(0, 100);
37         // 在位置0處插入long
38         sbuilder.insert(0, 12345L);
39         // 在位置0處插入StringBuilder對象
40         sbuilder.insert(0, new StringBuilder("StringBuilder"));
41         // 在位置0處插入StringBuilder對象。6表示被在位置0處插入對象的起始位置(包括)，13是結束位置(不包括)
42         sbuilder.insert(0, new StringBuilder("STRINGBUILDER"), 6, 13);
43         // 在位置0處插入StringBuffer對象。
44         sbuilder.insert(0, new StringBuffer("StringBuffer"));
45         // 在位置0處插入StringBuffer對象。6表示被在位置0處插入對象的起始位置(包括)，12是結束位置(不包括)
46         sbuilder.insert(0, new StringBuffer("STRINGBUFFER"), 6, 12);
47         // 在位置0處插入String對象。
48         sbuilder.insert(0, "String");
49         // 在位置0處插入String對象。1表示被在位置0處插入對象的起始位置(包括)，6是結束位置(不包括)
50         sbuilder.insert(0, "0123456789", 1, 6);
51         sbuilder.insert(0, '\n');
52 
53         // 在位置0處插入Object對象。此處以HashMap為例
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 }

運行結果：

-------------------------------- testInsertAPIs -------------------------------
{3=three, 2=two, 1=one}
12345StringBUFFERStringBufferBUILDERStringBuilder12345100
true3.141591.414ABCabcde

2. StringBuilder 中追加(append)相關的API

源碼如下(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         // 追加字符數組
24         sbuilder.append(new char[]{'a','b','c','d','e'});
25         // 追加字符數組。0表示字符數組起始位置，3表示長度
26         sbuilder.append(new char[]{'A','B','C','D','E'}, 0, 3);
27         // 追加float
28         sbuilder.append(1.414f);
29         // 追加double
30         sbuilder.append(3.14159d);
31         // 追加boolean
32         sbuilder.append(true);
33         // 追加char
34         sbuilder.append('\n');
35         // 追加int
36         sbuilder.append(100);
37         // 追加long
38         sbuilder.append(12345L);
39         // 追加StringBuilder對象
40         sbuilder.append(new StringBuilder("StringBuilder"));
41         // 追加StringBuilder對象。6表示被追加對象的起始位置(包括)，13是結束位置(不包括)
42         sbuilder.append(new StringBuilder("STRINGBUILDER"), 6, 13);
43         // 追加StringBuffer對象。
44         sbuilder.append(new StringBuffer("StringBuffer"));
45         // 追加StringBuffer對象。6表示被追加對象的起始位置(包括)，12是結束位置(不包括)
46         sbuilder.append(new StringBuffer("STRINGBUFFER"), 6, 12);
47         // 追加String對象。
48         sbuilder.append("String");
49         // 追加String對象。1表示被追加對象的起始位置(包括)，6是結束位置(不包括)
50         sbuilder.append("0123456789", 1, 6);
51         sbuilder.append('\n');
52 
53         // 追加Object對象。此處以HashMap為例
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編碼
62         sbuilder.appendCodePoint(0x5b57);    // 0x5b57是“字”的unicode編碼
63         sbuilder.appendCodePoint(0x7b26);    // 0x7b26是“符”的unicode編碼
64         sbuilder.appendCodePoint(0x7f16);    // 0x7f16是“編”的unicode編碼
65         sbuilder.appendCodePoint(0x7801);    // 0x7801是“碼”的unicode編碼
66 
67         System.out.printf("%s\n\n", sbuilder);
68     }
69 }

運行結果：

-------------------------------- testAppendAPIs -------------------------------
abcdeABC1.4143.14159true
10012345StringBuilderBUILDERStringBufferBUFFERString12345
{3=three, 2=two, 1=one}
字符編碼

3. StringBuilder 中替換(replace)相關的API

源碼如下(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 }

運行結果：

-------------------------------- testReplaceAPIs ------------------------------
sbuilder=ABCDE3456789
sbuilder=9876543210
sbuilder=M123456789

4. StringBuilder 中刪除(delete)相關的API

源碼如下(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         // 刪除位置0的字符，剩余字符是“123456789”。
24         sbuilder.deleteCharAt(0);
25         // 刪除位置3(包括)到位置6(不包括)之間的字符，剩余字符是“123789”。
26         sbuilder.delete(3,6);
27 
28         // 獲取sb中從位置1開始的字符串
29         String str1 = sbuilder.substring(1);
30         // 獲取sb中從位置3(包括)到位置5(不包括)之間的字符串
31         String str2 = sbuilder.substring(3, 5);
32         // 獲取sb中從位置3(包括)到位置5(不包括)之間的字符串，獲取的對象是CharSequence對象，此處轉型為String
33         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 }

運行結果：

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

5. StringBuilder 中index相關的API

源碼如下(StringBuilderIndexTest.java):

 1 /**
 2  * StringBuilder 中index相關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相關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. 從前往后，找出"bc"第一次出現的位置
24         System.out.printf("%-30s = %d\n", "sbuilder.indexOf(\"bc\")", sbuilder.indexOf("bc"));
25 
26         // 2. 從位置5開始，從前往后，找出"bc"第一次出現的位置
27         System.out.printf("%-30s = %d\n", "sbuilder.indexOf(\"bc\", 5)", sbuilder.indexOf("bc", 5));
28 
29         // 3. 從后往前，找出"bc"第一次出現的位置
30         System.out.printf("%-30s = %d\n", "sbuilder.lastIndexOf(\"bc\")", sbuilder.lastIndexOf("bc"));
31 
32         // 4. 從位置4開始，從后往前，找出"bc"第一次出現的位置
33         System.out.printf("%-30s = %d\n", "sbuilder.lastIndexOf(\"bc\", 4)", sbuilder.lastIndexOf("bc", 4));
34 
35         System.out.println();
36     }
37 }

運行結果：

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

6. StringBuilder 剩余的API

源碼如下(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 }

運行結果：

-------------------------------- testOtherAPIs --------------------------------
cap=26
c=6
carr[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幾個示例的完整的StringBuilder演示程序，源碼如下(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相關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. 從前往后，找出"bc"第一次出現的位置
 53         System.out.printf("%-30s = %d\n", "sbuilder.indexOf(\"bc\")", sbuilder.indexOf("bc"));
 54 
 55         // 2. 從位置5開始，從前往后，找出"bc"第一次出現的位置
 56         System.out.printf("%-30s = %d\n", "sbuilder.indexOf(\"bc\", 5)", sbuilder.indexOf("bc", 5));
 57 
 58         // 3. 從后往前，找出"bc"第一次出現的位置
 59         System.out.printf("%-30s = %d\n", "sbuilder.lastIndexOf(\"bc\")", sbuilder.lastIndexOf("bc"));
 60 
 61         // 4. 從位置4開始，從后往前，找出"bc"第一次出現的位置
 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         // 刪除位置0的字符，剩余字符是“123456789”。
101         sbuilder.deleteCharAt(0);
102         // 刪除位置3(包括)到位置6(不包括)之間的字符，剩余字符是“123789”。
103         sbuilder.delete(3,6);
104 
105         // 獲取sb中從位置1開始的字符串
106         String str1 = sbuilder.substring(1);
107         // 獲取sb中從位置3(包括)到位置5(不包括)之間的字符串
108         String str2 = sbuilder.substring(3, 5);
109         // 獲取sb中從位置3(包括)到位置5(不包括)之間的字符串，獲取的對象是CharSequence對象，此處轉型為String
110         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處插入字符數組
126         sbuilder.insert(0, new char[]{'a','b','c','d','e'});
127         // 在位置0處插入字符數組。0表示字符數組起始位置，3表示長度
128         sbuilder.insert(0, new char[]{'A','B','C','D','E'}, 0, 3);
129         // 在位置0處插入float
130         sbuilder.insert(0, 1.414f);
131         // 在位置0處插入double
132         sbuilder.insert(0, 3.14159d);
133         // 在位置0處插入boolean
134         sbuilder.insert(0, true);
135         // 在位置0處插入char
136         sbuilder.insert(0, '\n');
137         // 在位置0處插入int
138         sbuilder.insert(0, 100);
139         // 在位置0處插入long
140         sbuilder.insert(0, 12345L);
141         // 在位置0處插入StringBuilder對象
142         sbuilder.insert(0, new StringBuilder("StringBuilder"));
143         // 在位置0處插入StringBuilder對象。6表示被在位置0處插入對象的起始位置(包括)，13是結束位置(不包括)
144         sbuilder.insert(0, new StringBuilder("STRINGBUILDER"), 6, 13);
145         // 在位置0處插入StringBuffer對象。
146         sbuilder.insert(0, new StringBuffer("StringBuffer"));
147         // 在位置0處插入StringBuffer對象。6表示被在位置0處插入對象的起始位置(包括)，12是結束位置(不包括)
148         sbuilder.insert(0, new StringBuffer("STRINGBUFFER"), 6, 12);
149         // 在位置0處插入String對象。
150         sbuilder.insert(0, "String");
151         // 在位置0處插入String對象。1表示被在位置0處插入對象的起始位置(包括)，6是結束位置(不包括)
152         sbuilder.insert(0, "0123456789", 1, 6);
153         sbuilder.insert(0, '\n');
154 
155         // 在位置0處插入Object對象。此處以HashMap為例
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         // 追加字符數組
175         sbuilder.append(new char[]{'a','b','c','d','e'});
176         // 追加字符數組。0表示字符數組起始位置，3表示長度
177         sbuilder.append(new char[]{'A','B','C','D','E'}, 0, 3);
178         // 追加float
179         sbuilder.append(1.414f);
180         // 追加double
181         sbuilder.append(3.14159d);
182         // 追加boolean
183         sbuilder.append(true);
184         // 追加char
185         sbuilder.append('\n');
186         // 追加int
187         sbuilder.append(100);
188         // 追加long
189         sbuilder.append(12345L);
190         // 追加StringBuilder對象
191         sbuilder.append(new StringBuilder("StringBuilder"));
192         // 追加StringBuilder對象。6表示被追加對象的起始位置(包括)，13是結束位置(不包括)
193         sbuilder.append(new StringBuilder("STRINGBUILDER"), 6, 13);
194         // 追加StringBuffer對象。
195         sbuilder.append(new StringBuffer("StringBuffer"));
196         // 追加StringBuffer對象。6表示被追加對象的起始位置(包括)，12是結束位置(不包括)
197         sbuilder.append(new StringBuffer("STRINGBUFFER"), 6, 12);
198         // 追加String對象。
199         sbuilder.append("String");
200         // 追加String對象。1表示被追加對象的起始位置(包括)，6是結束位置(不包括)
201         sbuilder.append("0123456789", 1, 6);
202         sbuilder.append('\n');
203 
204         // 追加Object對象。此處以HashMap為例
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編碼
213         sbuilder.appendCodePoint(0x5b57);    // 0x5b57是“字”的unicode編碼
214         sbuilder.appendCodePoint(0x7b26);    // 0x7b26是“符”的unicode編碼
215         sbuilder.appendCodePoint(0x7f16);    // 0x7f16是“編”的unicode編碼
216         sbuilder.appendCodePoint(0x7801);    // 0x7801是“碼”的unicode編碼
217 
218         System.out.printf("%s\n\n", sbuilder);
219     }
220 }

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