How can I write an anonymous function in Java?

Question

Is it even possible?

Answer 1

With the introduction of lambda expression in Java 8 you can now have anonymous methods.

Say I have a class Alpha and I want to filter Alphas on a specific condition. To do this you can use a Predicate. This is a functional interface which has a method test that accepts an Alpha and returns a boolean.

Assuming that the filter method has this signature:

List filter(Predicate filterPredicate)

With the old anonymous class solution you would need to something like:

filter(new Predicate() {
   boolean test(Alpha alpha) {
      return alpha.centauri > 1;
   }
});

With the Java 8 lambdas you can do:

filter(alpha -> alpha.centauri > 1);

For more detailed information see the Lambda Expressions tutorial