### Question:
MultiValueMap extends HashMap<K, V> { @Override public V put(K key, V value){ return super.put(key, value); }  V add(K key, V value); @Override V put(K key, V value); Set<java.util.Map.Entry<K, V>> stream();  }### Answer:
@Test public void itShouldPut() { MultiValueMap<String, MultiValue> mvm = new MultiValueMap<>(); MultiValue<String,String> mv = new MultiValue<>("Test", "This is a test"); mvm.put("Test", mv); Assert.assertEquals("This is a test", mvm.get("Test").getValues().toArray()[0]); }