stringbuffer.java

gcc的组建

   * @param sequence the <code>CharSequence</code> to insert
   * @param start the starting index of the subsequence
   * @param end one past the ending index of the subsequence
   * @return this <code>StringBuffer</code>
   * @throws IndexOutOfBoundsException if offset, start,
   * or end are out of bounds
   * @since 1.5
   */
  public synchronized StringBuffer insert(int offset, CharSequence sequence,
					  int start, int end)
  {
    if (sequence == null)
      sequence = "null";
    if (start < 0 || end < 0 || start > end || end > sequence.length())
      throw new IndexOutOfBoundsException();
    int len = end - start;
    ensureCapacity_unsynchronized(count + len);
    VMSystem.arraycopy(value, offset, value, offset + len, count - offset);
    for (int i = start; i < end; ++i)
      value[offset++] = sequence.charAt(i);
    count += len;
    return this;
  }

  /**
   * Insert the <code>char[]</code> argument into this
   * <code>StringBuffer</code>.
   *
   * @param offset the place to insert in this buffer
   * @param data the <code>char[]</code> to insert
   * @return this <code>StringBuffer</code>
   * @throws NullPointerException if <code>data</code> is <code>null</code>
   * @throws StringIndexOutOfBoundsException if offset is out of bounds
   * @see #insert(int, char[], int, int)
   */
  public StringBuffer insert(int offset, char[] data)
  {
    return insert(offset, data, 0, data.length);
  }

  /**
   * 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 in this buffer
   * @param bool the <code>boolean</code> to convert and insert
   * @return this <code>StringBuffer</code>
   * @throws StringIndexOutOfBoundsException if offset is out of bounds
   * @see String#valueOf(boolean)
   */
  public StringBuffer insert(int offset, boolean bool)
  {
    return insert(offset, bool ? "true" : "false");
  }

  /**
   * Insert the <code>char</code> argument into this <code>StringBuffer</code>.
   *
   * @param offset the place to insert in this buffer
   * @param ch the <code>char</code> to insert
   * @return this <code>StringBuffer</code>
   * @throws StringIndexOutOfBoundsException if offset is out of bounds
   */
  public synchronized StringBuffer insert(int offset, char ch)
  {
    if (offset < 0 || offset > count)
      throw new StringIndexOutOfBoundsException(offset);
    ensureCapacity_unsynchronized(count + 1);
    VMSystem.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 in this buffer
   * @param inum the <code>int</code> to convert and insert
   * @return this <code>StringBuffer</code>
   * @throws StringIndexOutOfBoundsException if offset is out of bounds
   * @see String#valueOf(int)
   */
  public StringBuffer insert(int offset, int 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 in this buffer
   * @param lnum the <code>long</code> to convert and insert
   * @return this <code>StringBuffer</code>
   * @throws StringIndexOutOfBoundsException if offset is out of bounds
   * @see String#valueOf(long)
   */
  public StringBuffer insert(int offset, long lnum)
  {
    return insert(offset, Long.toString(lnum, 10));
  }

  /**
   * 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 in this buffer
   * @param fnum the <code>float</code> to convert and insert
   * @return this <code>StringBuffer</code>
   * @throws StringIndexOutOfBoundsException if offset is out of bounds
   * @see String#valueOf(float)
   */
  public StringBuffer insert(int offset, float fnum)
  {
    return insert(offset, Float.toString(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 in this buffer
   * @param dnum the <code>double</code> to convert and insert
   * @return this <code>StringBuffer</code>
   * @throws StringIndexOutOfBoundsException if offset is out of bounds
   * @see String#valueOf(double)
   */
  public StringBuffer insert(int offset, double dnum)
  {
    return insert(offset, Double.toString(dnum));
  }

  /**
   * Finds the first instance of a substring in this StringBuffer.
   *
   * @param str String to find
   * @return location (base 0) of the String, or -1 if not found
   * @throws NullPointerException if str is null
   * @see #indexOf(String, int)
   * @since 1.4
   */
  public int indexOf(String str)
  {
    return indexOf(str, 0);
  }

  /**
   * Finds the first instance of a String in this StringBuffer, starting at
   * a given index.  If starting index is less than 0, the search starts at
   * the beginning of this String.  If the starting index is greater than the
   * length of this String, or the substring is not found, -1 is returned.
   *
   * @param str String to find
   * @param fromIndex index to start the search
   * @return location (base 0) of the String, or -1 if not found
   * @throws NullPointerException if str is null
   * @since 1.4
   */
  public synchronized int indexOf(String str, int fromIndex)
  {
    if (fromIndex < 0)
      fromIndex = 0;
    int limit = count - str.count;
    for ( ; fromIndex <= limit; fromIndex++)
      if (regionMatches(fromIndex, str))
        return fromIndex;
    return -1;
  }

  /**
   * Finds the last instance of a substring in this StringBuffer.
   *
   * @param str String to find
   * @return location (base 0) of the String, or -1 if not found
   * @throws NullPointerException if str is null
   * @see #lastIndexOf(String, int)
   * @since 1.4
   */
  public int lastIndexOf(String str)
  {
    return lastIndexOf(str, count - str.count);
  }

  /**
   * Finds the last instance of a String in this StringBuffer, starting at a
   * given index.  If starting index is greater than the maximum valid index,
   * then the search begins at the end of this String.  If the starting index
   * is less than zero, or the substring is not found, -1 is returned.
   *
   * @param str String to find
   * @param fromIndex index to start the search
   * @return location (base 0) of the String, or -1 if not found
   * @throws NullPointerException if str is null
   * @since 1.4
   */
  public synchronized int lastIndexOf(String str, int fromIndex)
  {
    fromIndex = Math.min(fromIndex, count - str.count);
    for ( ; fromIndex >= 0; fromIndex--)
      if (regionMatches(fromIndex, str))
        return fromIndex;
    return -1;
  }

  /**
   * Reverse the characters in this StringBuffer. The same sequence of
   * characters exists, but in the reverse index ordering.
   *
   * @return this <code>StringBuffer</code>
   */
  public synchronized StringBuffer reverse()
  {
    // Call ensureCapacity to enforce copy-on-write.
    ensureCapacity_unsynchronized(count);
    for (int i = count >> 1, j = count - i; --i >= 0; ++j)
      {
        char c = value[i];
        value[i] = value[j];
        value[j] = c;
      }
    return this;
  }

  /**
   * Convert this <code>StringBuffer</code> to a <code>String</code>. The
   * String is composed of the characters currently in this StringBuffer. Note
   * that the result is a copy, and that future modifications to this buffer
   * do not affect the String.
   *
   * @return the characters in this StringBuffer
   */
  public String toString()
  {
    // The string will set this.shared = true.
    return new String(this);
  }

  /**
   * This may reduce the amount of memory used by the StringBuffer,
   * by resizing the internal array to remove unused space.  However,
   * this method is not required to resize, so this behavior cannot
   * be relied upon.
   * @since 1.5
   */
  public synchronized void trimToSize()
  {
    int wouldSave = value.length - count;
    // Some random heuristics: if we save less than 20 characters, who
    // cares.
    if (wouldSave < 20)
      return;
    // If we save more than 200 characters, shrink.
    // If we save more than 1/4 of the buffer, shrink.
    if (wouldSave > 200 || wouldSave * 4 > value.length)
      {
	char[] newValue = new char[count];
	VMSystem.arraycopy(value, 0, newValue, 0, count);
	value = newValue;
      }
  }

  /**
   * Return the number of code points between two indices in the
   * <code>StringBuffer</code>.  An unpaired surrogate counts as a
   * code point for this purpose.  Characters outside the indicated
   * range are not examined, even if the range ends in the middle of a
   * surrogate pair.
   *
   * @param start the starting index
   * @param end one past the ending index
   * @return the number of code points
   * @since 1.5
   */
  public synchronized int codePointCount(int start, int end)
  {
    if (start < 0 || end >= count || start > end)
      throw new StringIndexOutOfBoundsException();

    int count = 0;
    while (start < end)
      {
	char base = value[start];
	if (base < Character.MIN_HIGH_SURROGATE
	    || base > Character.MAX_HIGH_SURROGATE
	    || start == end
	    || start == count
	    || value[start + 1] < Character.MIN_LOW_SURROGATE
	    || value[start + 1] > Character.MAX_LOW_SURROGATE)
	  {
	    // Nothing.
	  }
	else
	  {
	    // Surrogate pair.
	    ++start;
	  }
	++start;
	++count;
      }
    return count;
  }

  /**
   * Starting at the given index, this counts forward by the indicated
   * number of code points, and then returns the resulting index.  An
   * unpaired surrogate counts as a single code point for this
   * purpose.
   *
   * @param start the starting index
   * @param codePoints the number of code points
   * @return the resulting index
   * @since 1.5
   */
  public synchronized int offsetByCodePoints(int start, int codePoints)
  {
    while (codePoints > 0)
      {
	char base = value[start];
	if (base < Character.MIN_HIGH_SURROGATE
	    || base > Character.MAX_HIGH_SURROGATE
	    || start == count
	    || value[start + 1] < Character.MIN_LOW_SURROGATE
	    || value[start + 1] > Character.MAX_LOW_SURROGATE)
	  {
	    // Nothing.
	  }
	else
	  {
	    // Surrogate pair.
	    ++start;
	  }
	++start;
	--codePoints;
      }
    return start;
  }

  /**
   * An unsynchronized version of ensureCapacity, used internally to avoid
   * the cost of a second lock on the same object. This also has the side
   * effect of duplicating the array, if it was shared (to form copy-on-write
   * semantics).
   *
   * @param minimumCapacity the minimum capacity
   * @see #ensureCapacity(int)
   */
  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];
        VMSystem.arraycopy(value, 0, nb, 0, count);
        value = nb;
        shared = false;
      }
  }

  /**
   * Predicate which determines if a substring of this matches another String
   * starting at a specified offset for each String and continuing for a
   * specified length. This is more efficient than creating a String to call
   * indexOf on.
   *
   * @param toffset index to start comparison at for this String
   * @param other non-null String to compare to region of this
   * @return true if regions match, false otherwise
   * @see #indexOf(String, int)
   * @see #lastIndexOf(String, int)
   * @see String#regionMatches(boolean, int, String, int, int)
   */
  private boolean regionMatches(int toffset, String other)
  {
    int len = other.count;
    int index = other.offset;
    while (--len >= 0)
      if (value[toffset++] != other.value[index++])
        return false;
    return true;
  }
}