如何在Java 8中将方法作为参数传递？ [英] How do I pass a method as a parameter in Java 8?

问题描述

我不明白如何使用lambdas将方法作为参数传递。

I don't understand how to use lambdas to pass a method as a parameter.

考虑以下（不编译）代码，如何将其完成为让它工作？

Considering the following (not compiling) code, how can I complete it to get it work ?

public class DumbTest {
    public class Stuff {
        public String getA() {
            return "a";
        }
        public String getB() {
            return "b";
        }
    }

    public String methodToPassA(Stuff stuff) {
        return stuff.getA();
    }

    public String methodToPassB(Stuff stuff) {
        return stuff.getB();
    }

    //MethodParameter is purely used to be comprehensive, nothing else...
    public void operateListWith(List<Stuff> listStuff, MethodParameter method) {
        for (Stuff stuff : listStuff) {
            System.out.println(method(stuff));
        }
    }

    public DumbTest() {
        List<Stuff> listStuff = new ArrayList<>();
        listStuff.add(new Stuff());
        listStuff.add(new Stuff());

        operateListWith(listStuff, methodToPassA);
        operateListWith(listStuff, methodToPassB);
    }

    public static void main(String[] args) {
        DumbTest l = new DumbTest();

    }
}

推荐答案

声明您的方法接受与您的方法签名匹配的现有功能接口类型的参数：

Declare your method to accept a parameter of an existing functional interface type which matches your method signature:

public void operateListWith(List<Stuff> listStuff, Function<Stuff, String> method) {
    for (Stuff stuff : listStuff) {
        System.out.println(method.apply(stuff));
    }
}

并按原样调用：

operateListWith(listStuff, this::methodToPassA);

作为进一步的见解，您不需要间接 methodToPassA ：

As a further insight, you don't need the indirection of methodToPassA:

operateListWith(listStuff, Stuff::getA);

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