Java function interface for Supplier<T> failed to compile non-lambda-CodePudding

I've got this:

import java.util.function.*;
public class FluentApi {
    public Integer myfunc(){
        return Integer.valueOf(1);
    }
    public void fSupplier(Supplier<Integer> si){
        System.out.println(si.get());
    }
    public void callFunc(){
        fSupplier(myfunc); // compilation failure
    }
}

It says: myfunc cannot be resolved to a variableJava(33554515)

If I change it to a lambda function then it compiles:

    public void callFunc(){
        fSupplier(()->Integer.valueOf(1));
    }

So what is the core difference here? How can I use a non-lambda implementation here?

Thanks.

CodePudding user response：

You will need to pass myfunc as a method reference.

Try this:

public void callFunc() {
    fSupplier(this::myfunc);
}

CodePudding user response：

Your method have one parameter of type Supplier<Integer> so you have three choices to pass as argument to this method (the idea is to pass an instance of a class who implements the functional interface Supplier):

A lambda expression

public void callFunc() {
    fSupplier(()->Integer.valueOf(1));
}

A method reference

public void callFunc() {
     fSupplier(this::myfunc);
 }

An anonymous inner class

 public void callFunc(){
     fSupplier(new Supplier<Integer>() {

         @Override
         public Integer get() {
             return Integer.valueOf(1);
         }
     }); 
 }