LinkedProperties extends Properties { @Override public boolean containsValue(Object value) { return linkMap.containsValue(value); }  @Override synchronized Object put(Object key, Object value); @Override synchronized boolean contains(Object value); @Override boolean containsValue(Object value); @Override synchronized Enumeration<Object> elements(); @Override Set<Map.Entry<Object, Object>> entrySet(); @Override synchronized void clear(); @Override synchronized boolean containsKey(Object key);  }
@Test public void containsValueTest() { assertThat(linkedProperties.contains("value"), is(false)); linkedProperties.put("key", "value"); assertThat(linkedProperties.containsValue("value"), is(true)); }