How to accept parameters in a new Callable instance passed as a function parameter

Question

I am new to Java and trying to pass a function as an argument that gets called when a certain event occurs. I came across Callable and found a few answers for similar problems but not this exactly.

Currently, my code is doing this

doSomething(new Callable<Void>() {
  public Void call() {
    System.out.println("callback called! ");
    return null;
  }
});

But I want this :

doSomething(new Callable<Void>() {
  public Void call(String foo) { // Want this function to accept parameters
    System.out.println("callback called with string " + foo);
    return null;
  }
});

Does this answer your question? [Is there a way to take an argument in a callable method?](https://stackoverflow.com/questions/9992992/is-there-a-way-to-take-an-argument-in-a-callable-method) — Anthony Cathers, Oct 01 '21 at 21:19

lkatiforis · Answer 1 · 2021-10-02T01:54:00.797

The java.util.function.Consumer functional interface is exactly what you are looking for: accepts a single argument and returns no output.

You need to do something like:

    doSomething(new Consumer<String>() {
        @Override
        public void accept(String foo) {
            System.out.println("Consumer called with string " + foo);
        }
    });

Or even better, replace it with a lambda:

doSomething(foo -> System.out.println("Consumer called with string " + foo));

doSomething looks like this:

void doSomething(Consumer<String> stringConsumer) {
    stringConsumer.accept("Hello!");
}

How to accept parameters in a new Callable instance passed as a function parameter

1 Answers1