FULL PRODUCT VERSION :
java version "1.6.0_14"
Java(TM) SE Runtime Environment (build 1.6.0_14-b08)
Java HotSpot(TM) 64-Bit Server VM (build 14.0-b16, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 6.0.6002]


A DESCRIPTION OF THE PROBLEM :
The Writer append methods for CharSequence have poor performance for CharBuffer. When call Writer#append(CharBuffer) the charbuffer is converted to a string (full copy of chars), then to a char array, then wrapped back into a CharBuffer inside the StreamEncoder.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The CharBuffer should be passed all the way through to the stream encoder

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
CharBufferdata = CharBuffer.allocate(4 * 1024);
    File file = new File("blah");
    FileWriter writer = new FileWriter(file);
    writer.append(data);
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Note: this only works for FileWriter, ideally it should be done in Writer. This is a hack to get inner array. Will not work for some CharBuffers without arrays.

private static class MyFileWriter extends FileWriter {

    public MyFileWriter(File file) throws IOException {
      super(file);
    }

    @Override
    public Writer append(CharSequence csq, int start, int end) throws IOException {
      if (csq instanceof CharBuffer) {
        CharBuffer buffer = (CharBuffer) csq;
        if (buffer.hasArray()) {
          char[] chars = buffer.array();
          int len = end - start;
          int off = start + buffer.arrayOffset();
          write(chars, off, len);
          return this;
        }
        
      }
      
      return super.append(csq, start, end);
    }

    @Override
    public Writer append(CharSequence csq) throws IOException {
      return append(csq, 0, csq.length());
    }
    
    
    
  }