Call another method B when method A is called

Is there a way in Java using reflection or any, to call a method or a class when a custom method is called.

I have a packed library.jar, in which Foo.class has method doThat(String a, MyObject b)

public class Foo {
    public Object doThat(String a, MyObject b) {
      // do something
      return null;
    }
}

I need a trigger my custom method Bar#doThis, when Foo#doThat is called.

public class Bar {
    public boolean doThis(String a, MyObject b) {
      // did it.
      return true;
    }
}

I will not be able to extract the jar and inject listeners. Foo.class is as similar as java.util.ArrayList or final class java.util.zip.ZipCoder