Java中的回调方法是什么? (该术语似乎被宽松地使用) [英] What is a callback method in Java? (Term seems to be used loosely)

问题描述

我不明白什么是回调方法，而且我听说人们很随意地使用该术语.在Java世界中，什么是回调方法?如果有人可以提供一些有关Java回调方法的示例代码并提供解释，那么这将对我的Java学习之旅大有帮助.

I don't understand what a callback method is and I have heard people use that term very loosely. In the Java world, what is a callback method? If someone could provide some example code of a Java callback method with an explanation, it would be a great help in my Java learning journey.

谢谢.

推荐答案

回调是一段代码，您可以将它作为参数传递给其他代码，以便其执行.由于Java尚不支持函数指针，因此它们被实现为Command对象.像

A callback is a piece of code that you pass as an argument to some other code so that it executes it. Since Java doesn't yet support function pointers, they are implemented as Command objects. Something like

public class Test {
    public static void main(String[] args) throws  Exception {
        new Test().doWork(new Callback() { // implementing class            
            @Override
            public void call() {
                System.out.println("callback called");
            }
        });
    }

    public void doWork(Callback callback) {
        System.out.println("doing work");
        callback.call();
    }

    public interface Callback {
        void call();
    }
}

回调通常会保留对某些状态的引用，这样才能真正有用.

A callback will usually hold reference to some state to actually be useful.

通过使回调实现具有对代码的所有依赖关系，您将获得代码与执行回调的代码之间的间接访问.

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