DatagramPacket.setData has the following definition:
 
   public synchronized void setData(byte[] buf) {
if (buf == null) {
throw new NullPointerException("null packet buffer");
}
this.buf = buf;

if (length > buf.length) {
setLength(buf.length);
}
    }

This is strange because it leaves offset unchanged, and only changes
length if buf.length is less than length. This is incosistent with
setData(byte[] buf, int offset, int length)
which sets both offset and length. The intuitive behavior for
setData(buf) would be that it be equivalent to
setData(buf, 0, buf.length), but it is not.

A minor doc error is that
    public synchronized void setData(byte[] buf, int offset, int length) {
says it is @since JDK1.1. This is not true, because this overload was
introduced in JDK1.2.