code: public static <K> NumberMap<K, Byte> newByteMap() {
  		return new NumberMap<K, Byte>() {
  			@Override
  			public void add(K key, Byte addend) {
  				put(key, (byte)(containsKey(key) ? get(key) + addend : addend));
  			}
  			@Override
  			public void sub(K key, Byte subtrahend) {
  				put(key, (byte)((containsKey(key) ? get(key) : 0) - subtrahend));
  			}
  		};
  	}
docs: Creates a NumberMap for Bytes.
  
  @param <K>
  @return NumberMap&lt;K, Byte&gt;