map key value 换位

test.java

private <T> Map<T,T> filp(Map<T,T> m) {
		Set<T> keys = m.keySet();
        Map<T,T> m2 = new HashMap<T,T>();
		for (T key : keys) {
			T value = m.get(key);
			m2.put(value, key);
		}
		return m2;
	}