Java tutorial
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; } }