StringBuffer


1   /*
2    * @(#)StringBuffer.java    1.99 04/07/15
3    *
4    * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
5    * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
6    */
7   
8   package java.lang;
9   
10  import sun.misc.FloatingDecimal;
11  
12  /**
13   * A thread-safe, mutable sequence of characters. 
14   * A string buffer is like a {@link String}, but can be modified. At any 
15   * point in time it contains some particular sequence of characters, but 
16   * the length and content of the sequence can be changed through certain 
17   * method calls.
18   * <p>
19   * String buffers are safe for use by multiple threads. The methods 
20   * are synchronized where necessary so that all the operations on any 
21   * particular instance behave as if they occur in some serial order 
22   * that is consistent with the order of the method calls made by each of 
23   * the individual threads involved.
24   * <p>
25   * The principal operations on a <code>StringBuffer</code> are the 
26   * <code>append</code> and <code>insert</code> methods, which are 
27   * overloaded so as to accept data of any type. Each effectively 
28   * converts a given datum to a string and then appends or inserts the 
29   * characters of that string to the string buffer. The 
30   * <code>append</code> method always adds these characters at the end 
31   * of the buffer; the <code>insert</code> method adds the characters at 
32   * a specified point. 
33   * <p>
34   * For example, if <code>z</code> refers to a string buffer object 
35   * whose current contents are "<code>start</code>", then 
36   * the method call <code>z.append("le")</code> would cause the string 
37   * buffer to contain "<code>startle</code>", whereas 
38   * <code>z.insert(4, "le")</code> would alter the string buffer to 
39   * contain "<code>starlet</code>". 
40   * <p>
41   * In general, if sb refers to an instance of a <code>StringBuffer</code>, 
42   * then <code>sb.append(x)</code> has the same effect as 
43   * <code>sb.insert(sb.length(),&nbsp;x)</code>.
44   * <p>
45   * Whenever an operation occurs involving a source sequence (such as
46   * appending or inserting from a source sequence) this class synchronizes
47   * only on the string buffer performing the operation, not on the source.
48   * <p>
49   * Every string buffer has a capacity. As long as the length of the 
50   * character sequence contained in the string buffer does not exceed 
51   * the capacity, it is not necessary to allocate a new internal 
52   * buffer array. If the internal buffer overflows, it is 
53   * automatically made larger. 
54   *
55   * As of  release JDK 5, this class has been supplemented with an equivalent 
56   * class designed for use by a single thread, {@link StringBuilder}.  The 
57   * <tt>StringBuilder</tt> class should generally be used in preference to 
58   * this one, as it supports all of the same operations but it is faster, as 
59   * it performs no synchronization.
60   *
61   * @author  Arthur van Hoff
62   * @version     1.99, 07/15/04
63   * @see     java.lang.StringBuilder
64   * @see     java.lang.String
65   * @since   JDK1.0
66   */
67   public final class StringBuffer
68      extends AbstractStringBuilder  
69      implements java.io.Serializable  , CharSequence  
70  {
71  
72      /** use serialVersionUID from JDK 1.0.2 for interoperability */
73      static final long serialVersionUID = 3388685877147921107L;
74  
75      /**
76       * Constructs a string buffer with no characters in it and an 
77       * initial capacity of 16 characters. 
78       */
79      public StringBuffer() {
80      super(16);
81      }
82  
83      /**
84       * Constructs a string buffer with no characters in it and 
85       * the specified initial capacity. 
86       *
87       * @param      capacity  the initial capacity.
88       * @exception  NegativeArraySizeException  if the <code>capacity</code>
89       *               argument is less than <code>0</code>.
90       */
91      public StringBuffer(int capacity) {
92      super(capacity);
93      }
94  
95      /**
96       * Constructs a string buffer initialized to the contents of the 
97       * specified string. The initial capacity of the string buffer is 
98       * <code>16</code> plus the length of the string argument.
99       *
100      * @param   str   the initial contents of the buffer.
101      * @exception NullPointerException if <code>str</code> is <code>null</code>
102      */
103     public StringBuffer(String   str) {
104     super(str.length() + 16);
105     append(str);
106     }
107 
108     /**
109      * Constructs a string buffer that contains the same characters
110      * as the specified <code>CharSequence</code>. The initial capacity of
111      * the string buffer is <code>16</code> plus the length of the
112      * <code>CharSequence</code> argument.
113      * <p>
114      * If the length of the specified <code>CharSequence</code> is
115      * less than or equal to zero, then an empty buffer of capacity
116      * <code>16</code> is returned.
117      *
118      * @param      seq   the sequence to copy.
119      * @exception NullPointerException if <code>seq</code> is <code>null</code>
120      * @since 1.5
121      */
122     public StringBuffer(CharSequence   seq) {
123         this(seq.length() + 16);
124         append(seq);
125     }
126 
127     public synchronized int length() {
128     return count;
129     }
130 
131     public synchronized int capacity() {
132     return value.length;
133     }
134 
135 
136     public synchronized void ensureCapacity(int minimumCapacity) {
137     if (minimumCapacity > value.length) {
138         expandCapacity(minimumCapacity);
139     }
140     }
141 
142     /**
143      * @since      1.5
144      */
145     public synchronized void trimToSize() {
146         super.trimToSize();
147     }
148 
149     /**
150      * @throws IndexOutOfBoundsException {@inheritDoc}
151      * @see        #length()
152      */
153     public synchronized void setLength(int newLength) {
154     super.setLength(newLength);
155     }
156 
157     /**
158      * @throws IndexOutOfBoundsException {@inheritDoc}
159      * @see        #length()
160      */
161     public synchronized char charAt(int index) {
162     if ((index < 0) || (index >= count))
163         throw new StringIndexOutOfBoundsException  (index);
164     return value[index];
165     }
166 
167     /**
168      * @since      1.5
169      */
170     public synchronized int codePointAt(int index) {
171         return super.codePointAt(index);
172     }
173 
174     /**
175      * @since     1.5
176      */
177     public synchronized int codePointBefore(int index) {
178         return super.codePointBefore(index);
179     }
180 
181     /**
182      * @since     1.5
183      */
184     public synchronized int codePointCount(int beginIndex, int endIndex) {
185     return super.codePointCount(beginIndex, endIndex);
186     }
187 
188     /**
189      * @since     1.5
190      */
191     public synchronized int offsetByCodePoints(int index, int codePointOffset) {
192     return super.offsetByCodePoints(index, codePointOffset);
193     }
194 
195     /**
196      * @throws NullPointerException {@inheritDoc}
197      * @throws IndexOutOfBoundsException {@inheritDoc}
198      */
199     public synchronized void getChars(int srcBegin, int srcEnd, char dst[],
200                                       int dstBegin)
201     {
202     super.getChars(srcBegin, srcEnd, dst, dstBegin);
203     }
204 
205     /**
206      * @throws IndexOutOfBoundsException {@inheritDoc}
207      * @see        #length()
208      */
209     public synchronized void setCharAt(int index, char ch) {
210     if ((index < 0) || (index >= count))
211         throw new StringIndexOutOfBoundsException  (index);
212     value[index] = ch;
213     }
214 
215     /**
216      * @see     java.lang.String#valueOf(java.lang.Object)
217      * @see     #append(java.lang.String)
218      */
219     public synchronized StringBuffer   append(Object   obj) {
220     super.append(String.valueOf(obj));
221         return this;
222     }
223 
224     public synchronized StringBuffer   append(String   str) {
225     super.append(str);
226         return this;
227     }
228 
229     /**
230      * Appends the specified <tt>StringBuffer</tt> to this sequence.
231      * <p>
232      * The characters of the <tt>StringBuffer</tt> argument are appended, 
233      * in order, to the contents of this <tt>StringBuffer</tt>, increasing the 
234      * length of this <tt>StringBuffer</tt> by the length of the argument. 
235      * If <tt>sb</tt> is <tt>null</tt>, then the four characters 
236      * <tt>"null"</tt> are appended to this <tt>StringBuffer</tt>.
237      * <p>
238      * Let <i>n</i> be the length of the old character sequence, the one 
239      * contained in the <tt>StringBuffer</tt> just prior to execution of the 
240      * <tt>append</tt> method. Then the character at index <i>k</i> in 
241      * the new character sequence is equal to the character at index <i>k</i> 
242      * in the old character sequence, if <i>k</i> is less than <i>n</i>; 
243      * otherwise, it is equal to the character at index <i>k-n</i> in the 
244      * argument <code>sb</code>.
245      * <p>
246      * This method synchronizes on <code>this</code> (the destination) 
247      * object but does not synchronize on the source (<code>sb</code>).
248      *
249      * @param   sb   the <tt>StringBuffer</tt> to append.
250      * @return  a reference to this object.
251      * @since 1.4
252      */
253     public synchronized StringBuffer   append(StringBuffer   sb) {
254         super.append(sb);
255         return this;
256     }
257 
258 
259     /**
260      * Appends the specified <code>CharSequence</code> to this
261      * sequence.
262      * <p>
263      * The characters of the <code>CharSequence</code> argument are appended, 
264      * in order, increasing the length of this sequence by the length of the 
265      * argument.
266      *
267      * <p>The result of this method is exactly the same as if it were an
268      * invocation of this.append(s, 0, s.length());
269      *
270      * <p>This method synchronizes on this (the destination) 
271      * object but does not synchronize on the source (<code>s</code>).
272      *
273      * <p>If <code>s</code> is <code>null</code>, then the four characters 
274      * <code>"null"</code> are appended.
275      *
276      * @param   s the <code>CharSequence</code> to append.
277      * @return  a reference to this object.
278      * @since 1.5
279      */
280     public StringBuffer   append(CharSequence   s) {
281         // Note, synchronization achieved via other invocations
282         if (s == null)
283             s = "null";
284         if (s instanceof String  )
285             return this.append((String  )s);
286         if (s instanceof StringBuffer  )
287             return this.append((StringBuffer  )s);
288         return this.append(s, 0, s.length());
289     }
290 
291     /**
292      * @throws IndexOutOfBoundsException {@inheritDoc}
293      * @since      1.5
294      */
295     public synchronized StringBuffer   append(CharSequence   s, int start, int end) 
296     {
297         super.append(s, start, end);
298         return this;
299     }
300 
301     public synchronized StringBuffer   append(char str[]) { 
302         super.append(str);
303         return this;
304     }
305 
306     public synchronized StringBuffer   append(char str[], int offset, int len) {
307         super.append(str, offset, len);
308         return this;
309     }
310 
311     /**
312      * @see     java.lang.String#valueOf(boolean)
313      * @see     #append(java.lang.String)
314      */
315     public synchronized StringBuffer   append(boolean b) {
316         super.append(b);
317         return this;
318     }
319 
320     public synchronized StringBuffer   append(char c) {
321         super.append(c);
322         return this;
323     }
324 
325     /**
326      * @see     java.lang.String#valueOf(int)
327      * @see     #append(java.lang.String)
328      */
329     public synchronized StringBuffer   append(int i) {
330     super.append(i);
331         return this;
332     }
333 
334     /**
335      * @since 1.5
336      */
337     public synchronized StringBuffer   appendCodePoint(int codePoint) {
338     super.appendCodePoint(codePoint);
339     return this;
340     }
341 
342     /**
343      * @see     java.lang.String#valueOf(long)
344      * @see     #append(java.lang.String)
345      */
346     public synchronized StringBuffer   append(long lng) {
347         super.append(lng);
348     return this;
349     }
350 
351     /**
352      * @see     java.lang.String#valueOf(float)
353      * @see     #append(java.lang.String)
354      */
355     public synchronized StringBuffer   append(float f) {
356         new FloatingDecimal(f).appendTo(this);
357     return this;
358     }
359 
360     /**
361      * @see     java.lang.String#valueOf(double)
362      * @see     #append(java.lang.String)
363      */
364     public synchronized StringBuffer   append(double d) {
365         new FloatingDecimal(d).appendTo(this);
366     return this;
367     }
368 
369     /**
370      * @throws StringIndexOutOfBoundsException {@inheritDoc}
371      * @since      1.2
372      */
373     public synchronized StringBuffer   delete(int start, int end) {
374         super.delete(start, end);
375         return this;
376     }
377 
378     /**
379      * @throws StringIndexOutOfBoundsException {@inheritDoc}
380      * @since      1.2
381      */
382     public synchronized StringBuffer   deleteCharAt(int index) {
383         super.deleteCharAt(index);
384         return this;
385     }
386 
387     /**
388      * @throws StringIndexOutOfBoundsException {@inheritDoc}
389      * @since      1.2
390      */
391     public synchronized StringBuffer   replace(int start, int end, String   str) {
392         super.replace(start, end, str);
393         return this;
394     }
395 
396     /**
397      * @throws StringIndexOutOfBoundsException {@inheritDoc}
398      * @since      1.2
399      */
400     public synchronized String   substring(int start) {
401         return substring(start, count);
402     }
403 
404     /**
405      * @throws IndexOutOfBoundsException {@inheritDoc}
406      * @since      1.4
407      */
408     public synchronized CharSequence   subSequence(int start, int end) {
409         return super.substring(start, end);
410     }
411 
412     /**
413      * @throws StringIndexOutOfBoundsException {@inheritDoc}
414      * @since      1.2
415      */
416     public synchronized String   substring(int start, int end) {
417         return super.substring(start, end);
418     }
419 
420     /**
421      * @throws StringIndexOutOfBoundsException {@inheritDoc}
422      * @since      1.2
423      */
424     public synchronized StringBuffer   insert(int index, char str[], int offset,
425                                             int len) 
426     {
427         super.insert(index, str, offset, len);
428         return this;
429     }
430 
431     /**
432      * @throws StringIndexOutOfBoundsException {@inheritDoc}
433      * @see        java.lang.String#valueOf(java.lang.Object)
434      * @see        #insert(int, java.lang.String)
435      * @see        #length()
436      */
437     public synchronized StringBuffer   insert(int offset, Object   obj) {
438     super.insert(offset, String.valueOf(obj));
439         return this;
440     }
441 
442     /**
443      * @throws StringIndexOutOfBoundsException {@inheritDoc}
444      * @see        #length()
445      */
446     public synchronized StringBuffer   insert(int offset, String   str) {
447         super.insert(offset, str);
448         return this;
449     }
450 
451     /**
452      * @throws StringIndexOutOfBoundsException {@inheritDoc}
453      */
454     public synchronized StringBuffer   insert(int offset, char str[]) {
455         super.insert(offset, str);
456     return this;
457     }
458 
459     /**
460      * @throws IndexOutOfBoundsException {@inheritDoc}
461      * @since      1.5
462      */
463     public StringBuffer   insert(int dstOffset, CharSequence   s) {
464         // Note, synchronization achieved via other invocations
465         if (s == null)
466             s = "null";
467         if (s instanceof String  )
468             return this.insert(dstOffset, (String  )s);
469         return this.insert(dstOffset, s, 0, s.length());
470     }
471 
472     /**
473      * @throws IndexOutOfBoundsException {@inheritDoc}
474      * @since      1.5
475      */
476     public synchronized StringBuffer   insert(int dstOffset, CharSequence   s, 
477                                             int start, int end)
478     {
479         super.insert(dstOffset, s, start, end);
480         return this;
481     }
482 
483     /**
484      * @throws StringIndexOutOfBoundsException {@inheritDoc}
485      * @see        java.lang.String#valueOf(boolean)
486      * @see        #insert(int, java.lang.String)
487      * @see        #length()
488      */
489     public StringBuffer   insert(int offset, boolean b) {
490     return insert(offset, String.valueOf(b));
491     }
492 
493     /**
494      * @throws IndexOutOfBoundsException {@inheritDoc}
495      * @see        #length()
496      */
497     public synchronized StringBuffer   insert(int offset, char c) {
498     super.insert(offset, c);
499     return this;
500     }
501 
502     /**
503      * @throws StringIndexOutOfBoundsException {@inheritDoc}
504      * @see        java.lang.String#valueOf(int)
505      * @see        #insert(int, java.lang.String)
506      * @see        #length()
507      */
508     public StringBuffer   insert(int offset, int i) {
509     return insert(offset, String.valueOf(i));
510     }
511 
512     /**
513      * @throws StringIndexOutOfBoundsException {@inheritDoc}
514      * @see        java.lang.String#valueOf(long)
515      * @see        #insert(int, java.lang.String)
516      * @see        #length()
517      */
518     public StringBuffer   insert(int offset, long l) {
519     return insert(offset, String.valueOf(l));
520     }
521 
522     /**
523      * @throws StringIndexOutOfBoundsException {@inheritDoc}
524      * @see        java.lang.String#valueOf(float)
525      * @see        #insert(int, java.lang.String)
526      * @see        #length()
527      */
528     public StringBuffer   insert(int offset, float f) {
529     return insert(offset, String.valueOf(f));
530     }
531 
532     /**
533      * @throws StringIndexOutOfBoundsException {@inheritDoc}
534      * @see        java.lang.String#valueOf(double)
535      * @see        #insert(int, java.lang.String)
536      * @see        #length()
537      */
538     public StringBuffer   insert(int offset, double d) {
539     return insert(offset, String.valueOf(d));
540     }
541 
542     /**
543      * @throws NullPointerException {@inheritDoc}
544      * @since      1.4
545      */
546     public int indexOf(String   str) {
547     return indexOf(str, 0);
548     }
549 
550     /**
551      * @throws NullPointerException {@inheritDoc}
552      * @since      1.4
553      */
554     public synchronized int indexOf(String   str, int fromIndex) {
555         return String.indexOf(value, 0, count,
556                               str.toCharArray(), 0, str.length(), fromIndex);
557     }
558 
559     /**
560      * @throws NullPointerException {@inheritDoc}
561      * @since      1.4
562      */
563     public int lastIndexOf(String   str) {
564         // Note, synchronization achieved via other invocations
565         return lastIndexOf(str, count);
566     }
567 
568     /**
569      * @throws NullPointerException {@inheritDoc}
570      * @since      1.4
571      */
572     public synchronized int lastIndexOf(String   str, int fromIndex) {
573         return String.lastIndexOf(value, 0, count,
574                               str.toCharArray(), 0, str.length(), fromIndex);
575     }
576 
577     /**
578      * @since   JDK1.0.2
579      */
580     public synchronized StringBuffer   reverse() {
581     super.reverse();
582     return this;
583     }
584 
585     public synchronized String   toString() {
586     return new String  (value, 0, count);
587     }
588 
589     /**
590      * Serializable fields for StringBuffer.
591      * 
592      * @serialField value  char[]
593      *              The backing character array of this StringBuffer.
594      * @serialField count int
595      *              The number of characters in this StringBuffer.
596      * @serialField shared  boolean
597      *              A flag indicating whether the backing array is shared. 
598      *              The value is ignored upon deserialization.
599      */
600     private static final java.io.ObjectStreamField  [] serialPersistentFields = 
601     { 
602         new java.io.ObjectStreamField  ("value", char[].class), 
603         new java.io.ObjectStreamField  ("count", Integer.TYPE),
604         new java.io.ObjectStreamField  ("shared", Boolean.TYPE),
605     };
606 
607     /**
608      * readObject is called to restore the state of the StringBuffer from
609      * a stream.
610      */
611     private synchronized void writeObject(java.io.ObjectOutputStream   s)
612         throws java.io.IOException   {
613         java.io.ObjectOutputStream.PutField fields = s.putFields();
614         fields.put("value", value);
615         fields.put("count", count);
616         fields.put("shared", false);
617         s.writeFields();
618     }
619 
620     /**
621      * readObject is called to restore the state of the StringBuffer from
622      * a stream.
623      */
624     private void readObject(java.io.ObjectInputStream   s)
625         throws java.io.IOException  , ClassNotFoundException   {
626         java.io.ObjectInputStream.GetField fields = s.readFields();
627         value = (char[])fields.get("value", null);
628         count = (int)fields.get("count", 0);
629     }
630 }
631
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