Question

This may be something common and trivial, but I seem to be having trouble finding a concrete answer. In C# there is a concept of delegates, which relates strongly to the idea of function pointers from C++. Is there a similar functionality in Java? Given that pointers are somewhat absent, what is the best way about this? And to be clear, we’re talking first class here.

Answer 1

The Java idiom for function-pointer-like functionality is an an anonymous class implementing an interface, e.g.

Collections.sort(list, new Comparator<MyClass>(){
    public int compare(MyClass a, MyClass b)
    {
        // compare objects
    }
});

Update: the above is necessary in Java versions prior to Java 8. Now we have much nicer alternatives, namely lambdas:

list.sort((a, b) -> a.isGreaterThan(b));

and method references:

list.sort(MyClass::isGreaterThan);