NothingDecorator implements StringDecorator { @Override public String decorate(String str) { return str; }  @Override String decorate(String str);  }
@Test public void testDecorate() { System.out.println("decorate"); String result = instance.decorate("a"); assertThat(result).isEqualTo("a"); result = instance.decorate(null); assertThat(result).isEqualTo(null); }