public static <K, V> Map<K, V> unmodifiableMap(final Map<? extends K, ? extends V> m) {
		return Collections.unmodifiableMap(m);
	}
public static < K , V > Map < K , V > unmodifiableMap ( final Map < ? extends K , ? extends V > m ) { return Collections . unmodifiableMap ( m ) ; }
返回包装后不可修改的Map.

如果尝试修改，会抛出UnsupportedOperationException

@see java.util.Collections#unmodifiableMap(Map)