java回调

A的a调用B的b，b执行完后会自己调用callback传入答案，实现回调

接口Callback

public interface Callback {
    void tellYourAnswer(String name,int answer);
}

老师-A方

public class Teacher implements Callback {
    private Student student;

    public Teacher(Student student) {
        this.student = student;
    }
                //提问题
    public void makeQuestion() {
        //加个线程-异步回调
        new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println("回答一下，这个问题");
                //学生计算，解答，参数是记录将答案告诉上级
                student.haveQuestion(Teacher.this);
            }
        }).start();
    }

//接口方法，得到学生的解答后执行
    @Override
    public void tellYourAnswer(String name, int answer) {
        System.out.println(name + " 同学，你的回答是 " + answer);
    }
}

学生-抽象成接口

public interface Student {
    void haveQuestion(Callback callback);
}

一个学生-计算

public class Rickey implements Student {
    private String name;

    public Rickey(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public void haveQuestion(Callback callback) {
        try{
            Thread.sleep((long) (Math.random()*2));
        }catch (InterruptedException e){
            e.printStackTrace();
        }
         //将答案告诉老师，回调
        callback.tellYourAnswer(this.getName(), (int) (Math.random()*10));
    }
}

测试：

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class CallbackTestTest {
    @org.junit.jupiter.api.Test
    public void myTest1() {
        Student rickey1 = new Rickey("r1");
        Student rickey2 = new Rickey("r2");
        Student rickey3 = new Rickey("r3");
        Student rickey4 = new Rickey("r4");
        Student rickey5 = new Rickey("r5");
        List<Student> list = new ArrayList<>();
        list.add(rickey1);
        list.add(rickey2);
        list.add(rickey3);
        list.add(rickey4);
        list.add(rickey5);

        for (Iterator<Student> it = list.iterator(); it.hasNext(); ) {
            Student r = it.next();
            Teacher teacher = new Teacher(r);
            teacher.makeQuestion();
        }

    }

参考博客：

同步调用/异步调用：

https://blog.csdn.net/o15277012330o/article/details/79271385

经典例子，直接概括

https://blog.csdn.net/xiaanming/article/details/8703708

同步调用/异步调用/回调：

https://www.cnblogs.com/xrq730/p/6424471.html