title: Is there a way to turn an existing interface into a functional interface?
body: <p>I am using an interface that looks something along the lines of this:</p>
  
  <pre><code>public interface ObjectListener {
      public void objectAdded(Object o);
      public void objectRemoved(Object o);
  }
  </code></pre>
  
  <p>And I am currently using an anonymous class to implement the interface, but I don't care about one of the two methods. Something along the lines of this:</p>
  
  <pre><code>someObject.addListener(new ObjectListener() {
  
      @Override
      public void objectAdded(Object o) {
          doSomething(o);
      }
  
      @Override
      public void objectRemoved(Object o) {}
  });
  </code></pre>
  
  <p>Now, I've been using the new lambda expressions in Java 8 wherever I'm able, and I would like to use the added simplicity in a situation like this. After all, I'm only implementing one of the methods, but since there are two methods in the interface, I can't use it in a lambda expression.</p>
  
  <p>Is there a way for me to get around this restriction?</p>