### Question:
EmptyConstructor implements EmptyTreeConstructor<E, MutableBinaryTreeNode<E>, MutableBinaryTreeImpl<E>> { @Override public Class<? extends Tree> forClass() { return MutableBinaryTreeImpl.class; }  @Override MutableBinaryTreeImpl<E> build(); @Override Class<? extends Tree> forClass();  }### Answer:
@Test public void forClass() { final EmptyConstructor<String> constructor = new EmptyConstructor<>(); assertEquals(MutableBinaryTreeImpl.class, constructor.forClass()); }