stringbuffer.java

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        System.arraycopy(value, index+1, value, index, count-index-1);
        count--;
        return this;
    }

    /**
     * Inserts the string representation of the <code>Object</code> 
     * argument into this string buffer. 
     * <p>
     * The second argument is converted to a string as if by the method 
     * <code>String.valueOf</code>, and the characters of that 
     * string are then inserted into this string buffer at the indicated 
     * offset. 
     * <p>
     * The offset argument must be greater than or equal to 
     * <code>0</code>, and less than or equal to the length of this 
     * string buffer. 
     *
     * @param      offset   the offset.
     * @param      obj      an <code>Object</code>.
     * @return     a reference to this <code>StringBuffer</code> object.
     * @exception  StringIndexOutOfBoundsException  if the offset is invalid.
     * @see        java.lang.String#valueOf(java.lang.Object)
     * @see        java.lang.StringBuffer#insert(int, java.lang.String)
     * @see        java.lang.StringBuffer#length()
     */
    public synchronized StringBuffer insert(int offset, Object obj) {
        return insert(offset, String.valueOf(obj));
    }

    /**
     * Inserts the string into this string buffer. 
     * <p>
     * The characters of the <code>String</code> argument are inserted, in 
     * order, into this string buffer at the indicated offset, moving up any 
     * characters originally above that position and increasing the length 
     * of this string buffer by the length of the argument. If 
     * <code>str</code> is <code>null</code>, then the four characters 
     * <code>"null"</code> are inserted into this string buffer.
     * <p>
     * The character at index <i>k</i> in the new character sequence is 
     * equal to:
     * <ul>
     * <li>the character at index <i>k</i> in the old character sequence, if 
     * <i>k</i> is less than <code>offset</code> 
     * <li>the character at index <i>k</i><code>-offset</code> in the 
     * argument <code>str</code>, if <i>k</i> is not less than 
     * <code>offset</code> but is less than <code>offset+str.length()</code> 
     * <li>the character at index <i>k</i><code>-str.length()</code> in the 
     * old character sequence, if <i>k</i> is not less than 
     * <code>offset+str.length()</code>
     * </ul><p>
     * The offset argument must be greater than or equal to 
     * <code>0</code>, and less than or equal to the length of this 
     * string buffer. 
     *
     * @param      offset   the offset.
     * @param      str      a string.
     * @return     a reference to this <code>StringBuffer</code> object.
     * @exception  StringIndexOutOfBoundsException  if the offset is invalid.
     * @see        java.lang.StringBuffer#length()
     */
    public synchronized StringBuffer insert(int offset, String str) {
        if ((offset < 0) || (offset > count)) {
            throw new StringIndexOutOfBoundsException();
        }

        if (str == null) {
            str = String.valueOf(str);
        }
        int len = str.length();
        int newcount = count + len;
        if (newcount > value.length)
            expandCapacity(newcount);
        else if (shared)
            copy();
        System.arraycopy(value, offset, value, offset + len, count - offset);
        str.getChars(0, len, value, offset);
        count = newcount;
        return this;
    }

    /**
     * Inserts the string representation of the <code>char</code> array 
     * argument into this string buffer. 
     * <p>
     * The characters of the array argument are inserted into the 
     * contents of this string buffer at the position indicated by 
     * <code>offset</code>. The length of this string buffer increases by 
     * the length of the argument. 
     * <p>
     * The overall effect is exactly as if the argument were converted to 
     * a string by the method {@link String#valueOf(char[])} and the 
     * characters of that string were then 
     * {@link #insert(int,String) inserted} into this 
     * <code>StringBuffer</code>  object at the position indicated by
     * <code>offset</code>.
     *
     * @param      offset   the offset.
     * @param      str      a character array.
     * @return     a reference to this <code>StringBuffer</code> object.
     * @exception  StringIndexOutOfBoundsException  if the offset is invalid.
     */
    public synchronized StringBuffer insert(int offset, char str[]) {
        if ((offset < 0) || (offset > count)) {
            throw new StringIndexOutOfBoundsException();
        }
        int len = str.length;
        int newcount = count + len;
        if (newcount > value.length)
            expandCapacity(newcount);
        else if (shared)
            copy();
        System.arraycopy(value, offset, value, offset + len, count - offset);
        System.arraycopy(str, 0, value, offset, len);
        count = newcount;
        return this;
    }

    /**
     * Inserts the string representation of the <code>boolean</code> 
     * argument into this string buffer. 
     * <p>
     * The second argument is converted to a string as if by the method 
     * <code>String.valueOf</code>, and the characters of that 
     * string are then inserted into this string buffer at the indicated 
     * offset. 
     * <p>
     * The offset argument must be greater than or equal to 
     * <code>0</code>, and less than or equal to the length of this 
     * string buffer. 
     *
     * @param      offset   the offset.
     * @param      b        a <code>boolean</code>.
     * @return     a reference to this <code>StringBuffer</code> object.
     * @exception  StringIndexOutOfBoundsException  if the offset is invalid.
     * @see        java.lang.String#valueOf(boolean)
     * @see        java.lang.StringBuffer#insert(int, java.lang.String)
     * @see        java.lang.StringBuffer#length()
     */
    public StringBuffer insert(int offset, boolean b) {
        return insert(offset, String.valueOf(b));
    }

    /**
     * Inserts the string representation of the <code>char</code> 
     * argument into this string buffer. 
     * <p>
     * The second argument is inserted into the contents of this string 
     * buffer at the position indicated by <code>offset</code>. The length 
     * of this string buffer increases by one. 
     * <p>
     * The overall effect is exactly as if the argument were converted to 
     * a string by the method {@link String#valueOf(char)} and the character 
     * in that string were then {@link #insert(int, String) inserted} into 
     * this <code>StringBuffer</code> object at the position indicated by
     * <code>offset</code>.
     * <p>
     * The offset argument must be greater than or equal to 
     * <code>0</code>, and less than or equal to the length of this 
     * string buffer. 
     *
     * @param      offset   the offset.
     * @param      c        a <code>char</code>.
     * @return     a reference to this <code>StringBuffer</code> object.
     * @exception  IndexOutOfBoundsException  if the offset is invalid.
     * @see        java.lang.StringBuffer#length()
     */
    public synchronized StringBuffer insert(int offset, char c) {
        int newcount = count + 1;
        if (newcount > value.length)
            expandCapacity(newcount);
        else if (shared)
            copy();
        System.arraycopy(value, offset, value, offset + 1, count - offset);
        value[offset] = c;
        count = newcount;
        return this;
    }

    /**
     * Inserts the string representation of the second <code>int</code> 
     * argument into this string buffer. 
     * <p>
     * The second argument is converted to a string as if by the method 
     * <code>String.valueOf</code>, and the characters of that 
     * string are then inserted into this string buffer at the indicated 
     * offset. 
     * <p>
     * The offset argument must be greater than or equal to 
     * <code>0</code>, and less than or equal to the length of this 
     * string buffer. 
     *
     * @param      offset   the offset.
     * @param      i        an <code>int</code>.
     * @return     a reference to this <code>StringBuffer</code> object.
     * @exception  StringIndexOutOfBoundsException  if the offset is invalid.
     * @see        java.lang.String#valueOf(int)
     * @see        java.lang.StringBuffer#insert(int, java.lang.String)
     * @see        java.lang.StringBuffer#length()
     */
    public StringBuffer insert(int offset, int i) {
        return insert(offset, String.valueOf(i));
    }

    /**
     * Inserts the string representation of the <code>long</code> 
     * argument into this string buffer. 
     * <p>
     * The second argument is converted to a string as if by the method 
     * <code>String.valueOf</code>, and the characters of that 
     * string are then inserted into this string buffer at the position 
     * indicated by <code>offset</code>. 
     * <p>
     * The offset argument must be greater than or equal to 
     * <code>0</code>, and less than or equal to the length of this 
     * string buffer. 
     *
     * @param      offset   the offset.
     * @param      l        a <code>long</code>.
     * @return     a reference to this <code>StringBuffer</code> object.
     * @exception  StringIndexOutOfBoundsException  if the offset is invalid.
     * @see        java.lang.String#valueOf(long)
     * @see        java.lang.StringBuffer#insert(int, java.lang.String)
     * @see        java.lang.StringBuffer#length()
     */
    public StringBuffer insert(int offset, long l) {
        return insert(offset, String.valueOf(l));
    }

    /**
     * The character sequence contained in this string buffer is 
     * replaced by the reverse of the sequence. 
     * <p>
     * Let <i>n</i> be the length of the old character sequence, the one 
     * contained in the string buffer just prior to execution of the 
     * <code>reverse</code> method. Then the character at index <i>k</i> in 
     * the new character sequence is equal to the character at index 
     * <i>n-k-1</i> in the old character sequence.
     *
     * @return  a reference to this <code>StringBuffer</code> object..
     * @since   JDK1.0.2
     */
    public synchronized StringBuffer reverse() {
        if (shared) copy();
        int n = count - 1;
        for (int j = (n-1) >> 1; j >= 0; --j) {
            char temp = value[j];
            value[j] = value[n - j];
            value[n - j] = temp;
        }
        return this;
    }

    /**
     * Converts to a string representing the data in this string buffer.
     * A new <code>String</code> object is allocated and initialized to 
     * contain the character sequence currently represented by this 
     * string buffer. This <code>String</code> is then returned. Subsequent 
     * changes to the string buffer do not affect the contents of the 
     * <code>String</code>. 
     * <p>
     * Implementation advice: This method can be coded so as to create a new
     * <code>String</code> object without allocating new memory to hold a 
     * copy of the character sequence. Instead, the string can share the 
     * memory used by the string buffer. Any subsequent operation that alters 
     * the content or capacity of the string buffer must then make a copy of 
     * the internal buffer at that time. This strategy is effective for 
     * reducing the amount of memory allocated by a string concatenation 
     * operation when it is implemented using a string buffer.
     *
     * @return  a string representation of the string buffer.
     */
    public native String toString();
/******
 *  public String toString() {
 *      return new String(this);
 *  }
 ******/

    //
    // The following two methods are needed by String to efficiently
    // convert a StringBuffer into a String.  They are not public.
    // They shouldn't be called by anyone but String.
    final void setShared() { shared = true; } 
    final char[] getValue() { return value; }

}