@Override
	public TreeEntryNode<K, V> putNode(K key, V value) {
		TreeEntryNode<K, V> target = nodes.get(key);
		if (ObjectUtil.isNotNull(target)) {
			final V oldVal = target.getValue();
			target.setValue(value);
			return target.copy(oldVal);
		}
		target = new TreeEntryNode<>(null, key, value);
		nodes.put(key, target);
		return null;
	}
@Test
	public void getNodeValueTest() {
		final ForestMap<String, String> map = new LinkedForestMap<>(false);
		map.putNode("a", "aaa");
		assertEquals("aaa", map.getNodeValue("a"));
		assertNull(map.getNodeValue("b"));
	}