Byte Counting OutputStream : OutputStream « File « Java Tutorial

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3. OutputStream

import java.io.IOException;
import java.io.OutputStream;

/**
 * Output stream that counts bytes written to it (but discards them).
 * 
 * @author Jonathan Locke
 */
public final class ByteCountingOutputStream extends OutputStream
{
  private long size;

  /**
   * @see java.io.OutputStream#write(int)
   */
  public void write(int b) throws IOException
  {
    size++;
  }

  /**
   * @see java.io.OutputStream#write(byte[], int, int)
   */
  public void write(byte b[], int off, int len) throws IOException
  {
    size += len;
  }

  /**
   * @return Number of bytes written to this stream
   */
  public long size()
  {
    return size;
  }
}