how to pass parameters to runnable method

Question

I have a function functionAcceptsMethod which accepts a runnable method as a parameter, I want to call functionAcceptsMethod by passing a method with parameters.

when I call functionAcceptsMethod by passing without parameters its fine but how to pass a function with parameters.

here is an example

 private void testFun() {
        functionAcceptsMethod(this::funWithoutParams);
        functionAcceptsMethod(this::funWithParams); // this where I need to pass params
        //functionAcceptsMethod(() -> funWithParams("abcd")); // I tried this, is this the right 
         //way?
    }

private void funWithoutParams() {
    //do something
}

private void funWithParams(String testString) {
    //do something
}

private  void functionAcceptsMethod(Runnable method) {
    method.run();
}

Answer 1

The right way is to have a version of your functionAcceptsMethod method with the parameter:

private void <T> functionAcceptsMethod(Consumer<T> method, T argument) {
    method.accept(argument);
}

Note that Runnable#run is a functional interface without a parameter, so you cannot use it here. You have to use Consumer. Now you can do this:

functionAcceptsMethod(this::funWithParams, "abc");

Check out java.util.function for more possibilities.

Answer 2

Yes, The approach

functionAcceptsMethod(() -> funWithParams("abcd"));

is ok, if your purpose is to just pass method reference and get args in parameters of functionAcceptsMethod method then use Consumer<T> as function receiver argument

As you wanted an example:

public static <T> void functionAcceptsMethod(Consumer<T> consumer, T t){
    consumer.accept(t);
}

This is a generic version and will accept any method that has single input parameter. and an example of usage:

public void example(){
    // Automatic type inferring
    functionAcceptsMethod(this::func, "f");
    functionAcceptsMethod(this::func2, 0);
    // Explicit type specification
    functionAcceptsMethod<Float>(this::func3, 0f);
}
public void func(String s){
    System.out.println(s);
}
public void func2(int i){
    System.out.println(i);
}
public void func3(float f){
}