code: @SuppressWarnings("rawtypes")
  	public static <K extends Comparable, V> TreeMap<K, V> newSortedMap() {
  		return new TreeMap<K, V>();
  	}
docs: 根据等号左边的类型，构造类型正确的TreeMap.
  
  @see com.google.common.collect.Maps#newTreeMap()