Patch: StringBuffer merge

Tom Tromey tromey@cygnus.com
Tue May 9 15:46:00 GMT 2000


I'm checking this in.  It merges the Classpath and libgcj StringBuffer
implementations.

I used libgcj's implementation as the base, since it is more efficient
and has fewer bugs.  From Classpath I brought over a nice bug fix
(involving the String(StringBuffer) constructor), missing methods from
JDK 1.2, and the JavaDoc comments.

I also reindented StringBuffer to conform to our current coding
standard.

I'm checking this in to Classpath as well.

2000-05-09  Tom Tromey  <tromey@cygnus.com>

	* java/lang/StringBuffer.java (toString): Don't mark buffer as
	shared.
	(insert(int,char[],int,int): New method.
	(delete): New method from Classpath.
	(deleteCharAt): Likewise.
	(substring): Likewise.
	(shared): No longer private.
	Added JavaDoc comments from Classpath.
	* java/lang/String.java (String(StringBuffer)): Ensure `buffer' is
	shared.

Tom

Index: java/lang/String.java
===================================================================
RCS file: /cvs/java/libgcj/libjava/java/lang/String.java,v
retrieving revision 1.7
diff -u -r1.7 String.java
--- String.java	2000/04/28 07:56:34	1.7
+++ String.java	2000/05/09 22:28:49
@@ -38,7 +38,11 @@
 
   public String (StringBuffer buffer)
   {
-    init (buffer.value, 0, buffer.count, true);
+    synchronized (buffer)
+      {
+	buffer.shared = true;
+	init (buffer.value, 0, buffer.count, true);
+      }
   }
 
   public String (char[] data)
Index: java/lang/StringBuffer.java
===================================================================
RCS file: /cvs/java/libgcj/libjava/java/lang/StringBuffer.java,v
retrieving revision 1.4
diff -u -r1.4 StringBuffer.java
--- StringBuffer.java	2000/04/09 04:52:43	1.4
+++ StringBuffer.java	2000/05/09 22:28:50
@@ -17,277 +17,651 @@
  */
 
 /* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3
+ * Updated using online JDK 1.2 docs.
+ * Believed complete and correct to JDK 1.2.
+ * Merged with Classpath.
  */
 
+/**
+ * <code>StringBuffer</code> represents a changeable <code>String</code>.
+ * It provides the operations required to modify the
+ * <code>StringBuffer</code> including insert, replace, delete, append,
+ * and reverse.
+ * <P>
+ *
+ * <code>StringBuffer</code>s are variable-length in nature, so even if
+ * you initialize them to a certain size, they can still grow larger than
+ * that.  <EM>Capacity</EM> indicates the number of characters the
+ * <code>StringBuffer</code> can have in it before it has to grow (growing
+ * the char array is an expensive operation involving <code>new</code>).
+ * <P>
+ *
+ * Incidentally, the String operator "+" actually is turned into a
+ * <code>StringBuffer</code> operation:
+ * <BR>
+ * <code>a + b</code>
+ * <BR>
+ * is the same as
+ * <BR>
+ * <code>new StringBuffer(a).append(b).toString()</code>.
+ *
+ * @implnote Classpath's StringBuffer is capable of sharing memory with
+ *           Strings for efficiency.  This will help in two instances:
+ *           first, when a StringBuffer is created from a String but is
+ *           never changed, and second, when a StringBuffer is converted
+ *           to a String and the StringBuffer is not changed after that.
+ *
+ * @since JDK1.0
+ * @author Paul Fisher
+ * @author John Keiser
+ * @author Tom Tromey
+ * @see java.lang.String
+ */
 public final class StringBuffer implements Serializable
 {
+  /** Append the <code>String</code> value of the argument to this <code>StringBuffer</code>.
+   *  Uses <code>String.valueOf()</code> to convert to
+   *  <code>String</code>.
+   *  @param bool the <code>boolean</code> to convert and append.
+   *  @return this <code>StringBuffer</code>.
+   *  @see java.lang.String#valueOf(boolean)
+   */
   public StringBuffer append (boolean bool)
-    {
-      return append (String.valueOf(bool));
-    }
-
+  {
+    return append (String.valueOf(bool));
+  }
+
+  /** Append the <code>char</code> to this <code>StringBuffer</code>.
+   *  @param c the <code>char</code> to append.
+   *  @return this <code>StringBuffer</code>.
+   */
   public synchronized StringBuffer append (char ch)
-    {
-      ensureCapacity_unsynchronized (count + 1);
-      value[count++] = ch;
-      return this;
-    }
-
+  {
+    ensureCapacity_unsynchronized (count + 1);
+    value[count++] = ch;
+    return this;
+  }
+
+  /** Append the <code>String</code> value of the argument to this <code>StringBuffer</code>.
+   *  Uses <code>String.valueOf()</code> to convert to
+   *  <code>String</code>.
+   *  @param inum the <code>int</code> to convert and append.
+   *  @return this <code>StringBuffer</code>.
+   *  @see java.lang.String#valueOf(int)
+   */
   public StringBuffer append (int inum)
-    {
-      return append (String.valueOf(inum));
-    }
-
+  {
+    return append (String.valueOf(inum));
+  }
+
+  /** Append the <code>String</code> value of the argument to this <code>StringBuffer</code>.
+   *  Uses <code>String.valueOf()</code> to convert to
+   *  <code>String</code>.
+   *  @param lnum the <code>long</code> to convert and append.
+   *  @return this <code>StringBuffer</code>.
+   *  @see java.lang.String#valueOf(long)
+   */
   public StringBuffer append (long lnum)
-    {
-      return append (String.valueOf(lnum));
-    }
-
+  {
+    return append (String.valueOf(lnum));
+  }
+
+  /** Append the <code>String</code> value of the argument to this <code>StringBuffer</code>.
+   *  Uses <code>String.valueOf()</code> to convert to
+   *  <code>String</code>.
+   *  @param fnum the <code>float</code> to convert and append.
+   *  @return this <code>StringBuffer</code>.
+   *  @see java.lang.String#valueOf(float)
+   */
   public StringBuffer append (float fnum)
-    {
-      return append (String.valueOf(fnum));
-    }
-
+  {
+    return append (String.valueOf(fnum));
+  }
+
+  /** Append the <code>String</code> value of the argument to this <code>StringBuffer</code>.
+   *  Uses <code>String.valueOf()</code> to convert to
+   *  <code>String</code>.
+   *  @param dnum the <code>double</code> to convert and append.
+   *  @return this <code>StringBuffer</code>.
+   *  @see java.lang.String#valueOf(double)
+   */
   public StringBuffer append (double dnum)
-    {
-      return append (String.valueOf(dnum));
-    }
-
+  {
+    return append (String.valueOf(dnum));
+  }
+
+  /** Append the <code>String</code> value of the argument to this <code>StringBuffer</code>.
+   *  Uses <code>String.valueOf()</code> to convert to
+   *  <code>String</code>.
+   *  @param obj the <code>Object</code> to convert and append.
+   *  @return this <code>StringBuffer</code>.
+   *  @see java.lang.String#valueOf(java.lang.Object)
+   */
   public StringBuffer append (Object obj)
-    {
-      return append (String.valueOf(obj));
-    }
-
+  {
+    return append (String.valueOf(obj));
+  }
+
+  /** Append the <code>String</code> to this <code>StringBuffer</code>.
+   *  @param str the <code>String</code> to append.
+   *  @return this <code>StringBuffer</code>.
+   */
   public synchronized StringBuffer append (String str)
-    {
-      if (str == null)
-	str = "null";
-      int len = str.length();
-      ensureCapacity_unsynchronized (count + len);
-      str.getChars(0, len, value, count);
-      count += len;
-      return this;
-    }
-
+  {
+    if (str == null)
+      str = "null";
+    int len = str.length();
+    ensureCapacity_unsynchronized (count + len);
+    str.getChars(0, len, value, count);
+    count += len;
+    return this;
+  }
+
+  /** Append the <code>char</code> array to this <code>StringBuffer</code>.
+   *  @param data the <code>char[]</code> to append.
+   *  @return this <code>StringBuffer</code>.
+   *  @exception NullPointerException if <code>str</code> is <code>null</code>.
+   */
   public StringBuffer append (char[] data)
-    {
-      return append (data, 0, data.length);
-    }
-
+  {
+    return append (data, 0, data.length);
+  }
+
+  /** Append the <code>char</code> array to this <code>StringBuffer</code>.
+   *  @param data the <code>char[]</code> to append.
+   *  @param offset the place to start grabbing characters from
+   *         <code>str</code>.
+   *  @param count the number of characters to get from <code>str</code>.
+   *  @return this <code>StringBuffer</code>.
+   *  @exception NullPointerException if <code>str</code> is <code>null</code>.
+   *  @exception IndexOutOfBoundsException if <code>offset</code> or
+   *             <code>offset+len</code> is out of range.
+   */
   public synchronized StringBuffer append (char[] data, int offset, int count)
-    {
-      ensureCapacity_unsynchronized (this.count + count);
-      System.arraycopy(data, offset, value, this.count, count);
-      this.count += count;
-      return this;
-    } 
-
+  {
+    ensureCapacity_unsynchronized (this.count + count);
+    System.arraycopy(data, offset, value, this.count, count);
+    this.count += count;
+    return this;
+  } 
+
+  /** Get the total number of characters this <code>StringBuffer</code>
+   *  can support before it must be grown.  Not to be confused with
+   *  <em>length</em>.
+   *  @return the capacity of this <code>StringBuffer</code>
+   *  @see #length()
+   *  @see #ensureCapacity(int)
+   */
   public int capacity ()
-    {
-      return value.length;
-    }
-
+  {
+    return value.length;
+  }
+
+  /** Get the character at the specified index.
+   *  @param index the index of the character to get, starting at 0.
+   *  @return the character at the specified index.
+   *  @exception IndexOutOfBoundsException if the desired character index
+   *             is not between 0 and length() - 1 (inclusive).
+   */
   public synchronized char charAt (int index)
-    {
-      if (index >= count)
-	throw new StringIndexOutOfBoundsException (index);
-      return value[index];
-    }
-
+  {
+    if (index >= count)
+      throw new StringIndexOutOfBoundsException (index);
+    return value[index];
+  }
+
+  /** Delete characters from this <code>StringBuffer</code>.
+   *  <code>delete(10, 12)</code> will delete 10 and 11, but not 12.
+   *  @param start the first character to delete.
+   *  @param end the index after the last character to delete.
+   *  @return this <code>StringBuffer</code>.
+   *  @exception StringIndexOutOfBoundsException if <code>start</code>
+   *             or <code>end-1</code> are out of bounds, or if
+   *             <code>start > end</code>.
+   */
+  public synchronized StringBuffer delete (int start, int end)
+  {
+    if (start < 0 || start > count || start > end)
+      throw new StringIndexOutOfBoundsException (start);
+    if (end > count)
+      end = count;
+    // This will unshare if required.
+    ensureCapacity_unsynchronized (count);
+    count -= (end - start);
+    System.arraycopy (value, end - 1, value, start, end - start);
+    return this;
+  }
+
+  /** Delete a character from this <code>StringBuffer</code>.
+   *  @param index the index of the character to delete.
+   *  @return this <code>StringBuffer</code>.
+   *  @exception StringIndexOutOfBoundsException if <code>index</code>
+   *             is out of bounds.
+   */
+  public StringBuffer deleteCharAt(int index)
+  {
+    return delete (index, index + 1);
+  }
+
+  /** Increase the capacity of this <code>StringBuffer</code>.
+   *  This will ensure that an expensive growing operation will not occur
+   *  until <code>minimumCapacity</code> is reached.
+   *  If the capacity is actually already greater than <code>minimumCapacity</code>
+   *  @param minimumCapacity the new capacity.
+   *  @see #capacity()
+   */
   public synchronized void ensureCapacity (int minimumCapacity)
-    {
-      if (shared || minimumCapacity > value.length)
-	{
-	  // We don't want to make a larger vector when `shared' is
-	  // set.  If we do, then setLength becomes very inefficient
-	  // when repeatedly reusing a StringBuffer in a loop.
-	  int max = (minimumCapacity > value.length
-		     ? value.length*2+2
-		     : value.length);
-	  minimumCapacity = (minimumCapacity < max ? max : minimumCapacity);
-	  char[] nb = new char[minimumCapacity];
-	  System.arraycopy(value, 0, nb, 0, count);
-	  value = nb;
-	  shared = false;
-	}
-    }
+  {
+    if (shared || minimumCapacity > value.length)
+      {
+	// We don't want to make a larger vector when `shared' is
+	// set.  If we do, then setLength becomes very inefficient
+	// when repeatedly reusing a StringBuffer in a loop.
+	int max = (minimumCapacity > value.length
+		   ? value.length*2+2
+		   : value.length);
+	minimumCapacity = (minimumCapacity < max ? max : minimumCapacity);
+	char[] nb = new char[minimumCapacity];
+	System.arraycopy(value, 0, nb, 0, count);
+	value = nb;
+	shared = false;
+      }
+  }
 
   // ensureCapacity is used by several synchronized methods in StringBuffer.
   // There's no need to synchronize again.
   private void ensureCapacity_unsynchronized (int minimumCapacity)
-    {
-      if (shared || minimumCapacity > value.length)
-	{
-	  // We don't want to make a larger vector when `shared' is
-	  // set.  If we do, then setLength becomes very inefficient
-	  // when repeatedly reusing a StringBuffer in a loop.
-	  int max = (minimumCapacity > value.length
-		     ? value.length*2+2
-		     : value.length);
-	  minimumCapacity = (minimumCapacity < max ? max : minimumCapacity);
-	  char[] nb = new char[minimumCapacity];
-	  System.arraycopy(value, 0, nb, 0, count);
-	  value = nb;
-	  shared = false;
-	}
-    }
-
+  {
+    if (shared || minimumCapacity > value.length)
+      {
+	// We don't want to make a larger vector when `shared' is
+	// set.  If we do, then setLength becomes very inefficient
+	// when repeatedly reusing a StringBuffer in a loop.
+	int max = (minimumCapacity > value.length
+		   ? value.length*2+2
+		   : value.length);
+	minimumCapacity = (minimumCapacity < max ? max : minimumCapacity);
+	char[] nb = new char[minimumCapacity];
+	System.arraycopy(value, 0, nb, 0, count);
+	value = nb;
+	shared = false;
+      }
+  }
+
+  /** Get the specified array of characters.
+   *  The characters will be copied into the array you pass in.
+   *  @param srcOffset the index to start copying from in the
+   *         <code>StringBuffer</code>.
+   *  @param srcEnd the number of characters to copy.
+   *  @param dst the array to copy into.
+   *  @param dstOffset the index to start copying into <code>dst</code>.
+   *  @exception NullPointerException if dst is null.
+   *  @exception IndexOutOfBoundsException if any source or target
+   *             indices are out of range.
+   *  @see java.lang.System#arrayCopy(java.lang.Object,int,java.lang.Object,int,int)
+   */
   public synchronized void getChars (int srcOffset, int srcEnd,
 				     char[] dst, int dstOffset)
-    {
-      if (srcOffset < 0 || srcOffset > srcEnd)
-	throw new StringIndexOutOfBoundsException (srcOffset);
-      int todo = srcEnd - srcOffset;
-      if (srcEnd > count || dstOffset + todo > count)
-	throw new StringIndexOutOfBoundsException (srcEnd);
-      System.arraycopy(value, srcOffset, dst, dstOffset, todo);
-    }
-
+  {
+    if (srcOffset < 0 || srcOffset > srcEnd)
+      throw new StringIndexOutOfBoundsException (srcOffset);
+    int todo = srcEnd - srcOffset;
+    if (srcEnd > count || dstOffset + todo > count)
+      throw new StringIndexOutOfBoundsException (srcEnd);
+    System.arraycopy(value, srcOffset, dst, dstOffset, todo);
+  }
+
+  /** Insert the <code>String</code> value of the argument into this <code>StringBuffer</code>.
+   *  Uses <code>String.valueOf()</code> to convert to
+   *  <code>String</code>.
+   *  @param offset the place to insert.
+   *  @param bool the <code>boolean</code> to convert and insert.
+   *  @return this <code>StringBuffer</code>.
+   *  @exception IndexOutOfBoundsException if <code>offset</code> is out
+   *             of range for this <code>StringBuffer</code>.
+   *  @see java.lang.String#valueOf(boolean)
+   */
   public StringBuffer insert (int offset, boolean bool)
-    {
-      return insert (offset, bool ? "true" : "false");
-    }
-
+  {
+    return insert (offset, bool ? "true" : "false");
+  }
+
+  /** Insert the <code>char</code> argument into this <code>StringBuffer</code>.
+   *  @param offset the place to insert.
+   *  @param ch the <code>char</code> to insert.
+   *  @return this <code>StringBuffer</code>.
+   *  @exception IndexOutOfBoundsException if <code>offset</code> is out
+   *             of range for this <code>StringBuffer</code>.
+   */
   public synchronized StringBuffer insert (int offset, char ch)
-    {
-      if (offset < 0 || offset > count)
-	throw new StringIndexOutOfBoundsException (offset);
-      ensureCapacity_unsynchronized (count+1);
-      System.arraycopy(value, offset, value, offset+1, count-offset);
-      value[offset] = ch;
-      count++;
-      return this;
-    }
-
+  {
+    if (offset < 0 || offset > count)
+      throw new StringIndexOutOfBoundsException (offset);
+    ensureCapacity_unsynchronized (count+1);
+    System.arraycopy(value, offset, value, offset+1, count-offset);
+    value[offset] = ch;
+    count++;
+    return this;
+  }
+
+  /** Insert the <code>String</code> value of the argument into this <code>StringBuffer</code>.
+   *  Uses <code>String.valueOf()</code> to convert to
+   *  <code>String</code>.
+   *  @param offset the place to insert.
+   *  @param inum the <code>int</code> to convert and insert.
+   *  @return this <code>StringBuffer</code>.
+   *  @exception IndexOutOfBoundsException if <code>offset</code> is out
+   *             of range for this <code>StringBuffer</code>.
+   *  @see java.lang.String#valueOf(int)
+   */
   public StringBuffer insert (int offset, int inum)
-    {
-      return insert (offset, String.valueOf(inum));
-    }
-
+  {
+    return insert (offset, String.valueOf(inum));
+  }
+
+  /** Insert the <code>String</code> value of the argument into this <code>StringBuffer</code>.
+   *  Uses <code>String.valueOf()</code> to convert to
+   *  <code>String</code>.
+   *  @param offset the place to insert.
+   *  @param lnum the <code>long</code> to convert and insert.
+   *  @return this <code>StringBuffer</code>.
+   *  @exception IndexOutOfBoundsException if <code>offset</code> is out
+   *             of range for this <code>StringBuffer</code>.
+   *  @see java.lang.String#valueOf(long)
+   */
   public StringBuffer insert (int offset, long lnum)
-    {
-      return insert (offset, String.valueOf(lnum));
-    }
-
+  {
+    return insert (offset, String.valueOf(lnum));
+  }
+
+  /** Insert the <code>String</code> value of the argument into this <code>StringBuffer</code>.
+   *  Uses <code>String.valueOf()</code> to convert to
+   *  <code>String</code>.
+   *  @param offset the place to insert.
+   *  @param fnum the <code>float</code> to convert and insert.
+   *  @return this <code>StringBuffer</code>.
+   *  @exception IndexOutOfBoundsException if <code>offset</code> is out
+   *             of range for this <code>StringBuffer</code>.
+   *  @see java.lang.String#valueOf(float)
+   */
   public StringBuffer insert (int offset, float fnum)
-    {
-      return insert (offset, String.valueOf(fnum));
-    }
-
+  {
+    return insert (offset, String.valueOf(fnum));
+  }
+
+  /** Insert the <code>String</code> value of the argument into this <code>StringBuffer</code>.
+   *  Uses <code>String.valueOf()</code> to convert to
+   *  <code>String</code>.
+   *  @param offset the place to insert.
+   *  @param dnum the <code>double</code> to convert and insert.
+   *  @return this <code>StringBuffer</code>.
+   *  @exception IndexOutOfBoundsException if <code>offset</code> is out
+   *             of range for this <code>StringBuffer</code>.
+   *  @see java.lang.String#valueOf(double)
+   */
   public StringBuffer insert (int offset, double dnum)
-    {
-      return insert (offset, String.valueOf(dnum));
-    }
-
+  {
+    return insert (offset, String.valueOf(dnum));
+  }
+
+  /** Insert the <code>String</code> value of the argument into this <code>StringBuffer</code>.
+   *  Uses <code>String.valueOf()</code> to convert to
+   *  <code>String</code>.
+   *  @param offset the place to insert.
+   *  @param obj the <code>Object</code> to convert and insert.
+   *  @return this <code>StringBuffer</code>.
+   *  @exception IndexOutOfBoundsException if <code>offset</code> is out
+   *             of range for this <code>StringBuffer</code>.
+   *  @see java.lang.String#valueOf(java.lang.Object)
+   */
   public StringBuffer insert (int offset, Object obj)
-    {
-      return insert (offset, String.valueOf(obj));
-    }
-
+  {
+    return insert (offset, String.valueOf(obj));
+  }
+
+  /** Insert the <code>String</code> argument into this <code>StringBuffer</code>.
+   *  @param offset the place to insert.
+   *  @param str the <code>String</code> to insert.
+   *  @return this <code>StringBuffer</code>.
+   *  @exception IndexOutOfBoundsException if <code>offset</code> is out
+   *             of range for this <code>StringBuffer</code>.
+   */
   public synchronized StringBuffer insert (int offset, String str)
-    {
-      if (offset < 0 || offset > count)
-	throw new StringIndexOutOfBoundsException (offset);
-      // Note that using `null' is from JDK 1.2.
-      if (str == null)
-	str = "null";
-      int len = str.length();
-      ensureCapacity_unsynchronized (count+len);
-      System.arraycopy(value, offset, value, offset+len, count-offset);
-      str.getChars(0, len, value, offset);
-      count += len;
-      return this;
-    }
-
-  public synchronized StringBuffer insert (int offset, char[] data)
-    {
-      if (offset < 0 || offset > count)
-	throw new StringIndexOutOfBoundsException (offset);
-      int len = data.length;
-      ensureCapacity_unsynchronized (count+len);
-      System.arraycopy(value, offset, value, offset+len, count-offset);
-      System.arraycopy(data, 0, value, offset, len);
-      count += len;
-      return this;
-    }
-
+  {
+    if (offset < 0 || offset > count)
+      throw new StringIndexOutOfBoundsException (offset);
+    // Note that using `null' is from JDK 1.2.
+    if (str == null)
+      str = "null";
+    int len = str.length();
+    ensureCapacity_unsynchronized (count+len);
+    System.arraycopy(value, offset, value, offset+len, count-offset);
+    str.getChars(0, len, value, offset);
+    count += len;
+    return this;
+  }
+
+  /** Insert the <code>char[]</code> argument into this
+   *  <code>StringBuffer</code>. 
+   *  @param offset the place to insert.
+   *  @param data the <code>char[]</code> to insert.
+   *  @return this <code>StringBuffer</code>.
+   *  @exception NullPointerException if <code>data</code> is
+   *             <code>null</code>.
+   *  @exception IndexOutOfBoundsException if <code>offset</code> is out
+   *             of range for this <code>StringBuffer</code>.
+   */
+  public StringBuffer insert (int offset, char[] data)
+  {
+    return insert (offset, data, 0, data.length);
+  }
+
+  /** Insert the <code>char[]</code> argument into this
+   *  <code>StringBuffer</code>.
+   *  @param offset the place to insert.
+   *  @param str the <code>char[]</code> to insert.
+   *  @param str_offset the index in <code>str</code> to start inserting
+   *         from.
+   *  @param len the number of characters to insert.
+   *  @return this <code>StringBuffer</code>.
+   *  @exception NullPointerException if <code>str</code> is <code>null</code>.
+   *  @exception IndexOutOfBoundsException if <code>offset</code> is out
+   *             of range, for this <code>StringBuffer</code>, or if
+   *             <code>str_offset</code> or <code>str_offset+len</code>
+   *             are out of range for <code>str</code>.
+   */
+  public synchronized StringBuffer insert(int offset, char[] str,
+					  int str_offset, int len)
+  {
+    if (offset < 0 || offset > count)
+      throw new StringIndexOutOfBoundsException (offset);
+    if (len < 0)
+      throw new StringIndexOutOfBoundsException (len);
+    if (str_offset < 0 || str_offset + len > str.length)
+      throw new StringIndexOutOfBoundsException (str_offset);
+    ensureCapacity_unsynchronized (count + len);
+    System.arraycopy(value, offset, value, offset + len, count - offset);
+    System.arraycopy(str, str_offset, value, offset, len);
+    count += len;
+    return this;
+  }
+
+  /** Get the length of the <code>String</code> this
+   *  <code>StringBuffer</code> would create.  Not to be confused with the
+   *  <em>capacity</em> of the <code>StringBuffer</code>.
+   *  @return the length of this <code>StringBuffer</code>.
+   *  @see #capacity()
+   *  @see #setLength()
+   */
   public int length ()
-    {
-      return count;
-    }
-
+  {
+    return count;
+  }
+
+  /** Delete a character from this <code>StringBuffer</code>.
+   *  @param index the index of the character to delete.
+   *  @return this <code>StringBuffer</code>.
+   *  @exception StringIndexOutOfBoundsException if <code>index</code>
+   *             is out of bounds.
+   */
+  public synchronized StringBuffer replace (int start, int end, String str)
+  {
+    // FIXME: this is inefficient.
+    delete (start, end);
+    return insert (start, str);
+  }
+
+  /** Reverse the characters in this StringBuffer.
+   *  @return this <code>StringBuffer</code>.
+   */
   public synchronized StringBuffer reverse ()
-    {
-      for (int i = 0; i < count / 2; ++i)
-	{
-	  char c = value[i];
-	  value[i] = value[count - i - 1];
-	  value[count - i - 1] = c;
-	}
-      return this;
-    }
-
+  {
+    for (int i = 0; i < count / 2; ++i)
+      {
+	char c = value[i];
+	value[i] = value[count - i - 1];
+	value[count - i - 1] = c;
+      }
+    return this;
+  }
+
+  /** Set the character at the specified index.
+   *  @param index the index of the character to set starting at 0.
+   *  @param ch the value to set that character to.
+   *  @exception IndexOutOfBoundsException if the specified character
+   *             index is not between 0 and length() - 1 (inclusive).
+   */
   public synchronized void setCharAt (int index, char ch)
-    {
-      if (index < 0 || index >= count)
-	throw new StringIndexOutOfBoundsException (index);
-      // Call ensureCapacity to enforce copy-on-write.
-      ensureCapacity_unsynchronized (count);
-      value[index] = ch;
-    }
-
+  {
+    if (index < 0 || index >= count)
+      throw new StringIndexOutOfBoundsException (index);
+    // Call ensureCapacity to enforce copy-on-write.
+    ensureCapacity_unsynchronized (count);
+    value[index] = ch;
+  }
+
+  /** Set the length of this StringBuffer.
+   *  <P>
+   *  If the new length is greater than the current length, all the new
+   *  characters are set to '\0'.
+   *  <P>
+   *  If the new length is less than the current length, the first
+   *  <code>newLength</code> characters of the old array will be
+   * @param newLength the new length
+   * @exception IndexOutOfBoundsException if the new length is
+   *            negative.
+   * @see #length()
+   */
   public synchronized void setLength (int newLength)
-    {
-      if (newLength < 0)
-	throw new StringIndexOutOfBoundsException (newLength);
-
-      ensureCapacity_unsynchronized (newLength);
-      for (int i = count; i < newLength; ++i)
-	value[i] = '\0';
-      count = newLength;
-    }
-
+  {
+    if (newLength < 0)
+      throw new StringIndexOutOfBoundsException (newLength);
+
+    ensureCapacity_unsynchronized (newLength);
+    for (int i = count; i < newLength; ++i)
+      value[i] = '\0';
+    count = newLength;
+  }
+
+  /** Create a new StringBuffer with default capacity 16.
+   *  @see JLS 20.13.1
+   */
   public StringBuffer ()
-    {
-      this (16);
-    }
-
+  {
+    this (DEFAULT_CAPACITY);
+  }
+
+  /** Create an empty <code>StringBuffer</code> with the specified initial capacity.
+   *  @param capacity the initial capacity.
+   */
   public StringBuffer (int capacity)
-    {
-      count = 0;
-      value = new char[capacity];
-      shared = false;
-    }
-
+  {
+    count = 0;
+    value = new char[capacity];
+    shared = false;
+  }
+
+  /** Create a new <code>StringBuffer</code> with the characters in the specified <code>String</code>.
+   *  Initial capacity will be the size of the String plus 16.
+   *  @param str the <code>String</code> to make a <code>StringBuffer</code> out of.
+   *  @XXX optimize for sharing.
+   */
   public StringBuffer (String str)
-    {
-      // The documentation is not clear, but experimentation with
-      // other implementations indicates that StringBuffer(null)
-      // should throw a NullPointerException.
-      count = str.length();
-      // JLS: The initial capacity of the string buffer is 16 plus the
-      // length of the argument string.
-      value = new char[count + 16];
-      str.getChars(0, count, value, 0);
-      shared = false;
-    }
-
+  {
+    // The documentation is not clear, but experimentation with
+    // other implementations indicates that StringBuffer(null)
+    // should throw a NullPointerException.
+    count = str.length();
+    // JLS: The initial capacity of the string buffer is 16 plus the
+    // length of the argument string.
+    value = new char[count + 16];
+    str.getChars(0, count, value, 0);
+    shared = false;
+  }
+
+  /**
+   * Creates a substring of this StringBuffer, starting at a specified index
+   * and ending at the end of this StringBuffer.
+   *
+   * @param beginIndex index to start substring (base 0)
+   * 
+   * @return new String which is a substring of this StringBuffer
+   *
+   * @exception StringIndexOutOfBoundsException 
+   *   if (beginIndex < 0 || beginIndex > this.length())
+   */
+  public String substring (int beginIndex)
+  {
+    return substring (beginIndex, count);
+  }
+
+  /**
+   * Creates a substring of this StringBuffer, starting at a specified index
+   * and ending at one character before a specified index.
+   *
+   * @param beginIndex index to start substring (base 0)
+   * @param endIndex index after the last character to be 
+   *   copied into the substring
+   * 
+   * @return new String which is a substring of this StringBuffer
+   *
+   * @exception StringIndexOutOfBoundsException 
+   *   if (beginIndex < 0 || endIndex > this.length() || beginIndex > endIndex)
+   */
+  public synchronized String substring (int beginIndex, int endIndex) 
+  {
+    if (beginIndex < 0 || endIndex > count || beginIndex > endIndex)
+      throw new StringIndexOutOfBoundsException ();
+    // FIXME: for libgcj it would be possible, and more efficient, to
+    // enable sharing here.
+    return new String (value, beginIndex, endIndex - beginIndex);
+  }
+
+  /** Convert this <code>StringBuffer</code> to a <code>String</code>.
+   *  @return the characters in this StringBuffer
+   */
   public String toString ()
-    {
-      shared = true;
-      return new String (this);
-    }
+  {
+    // Note: in libgcj this causes the StringBuffer to be shared.  In
+    // Classpath it does not.
+    return new String (this);
+  }
 
-  // The buffer.  Note that this has permissions set this way so that
-  // String can get the value.
-  char[] value;
-
   // Index of next available character.  Note that this has
   // permissions set this way so that String can get the value.
   int count;
 
+  // The buffer.  Note that this has permissions set this way so that
+  // String can get the value.
+  char[] value;
+
   // True if we need to copy the buffer before writing to it again.
   // FIXME: JDK 1.2 doesn't specify this.  The new buffer-growing
-  // semantics make this less useful in that case, too.
-  private boolean shared;
+  // semantics make this less useful in that case, too.  Note that
+  // this has permissions set this way so that String can get the
+  // value.
+  boolean shared;
+
+  static final long serialVersionUID = 3388685877147921107L;
+  private final static int DEFAULT_CAPACITY = 16; // JLS 20.13.1
 }


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