Asynchronous callback case of Java callback function

1. Callback function classification

Callback function distinction: synchronous callback and asynchronous callback

Synchronous callback: the meaning is only to complete the method call;

Asynchronous call: concurrency can be realized, and the main business thread can be released in time; asynchronous thread completes the work, executes callback function, and completes the aftermath work; the execution efficiency is improved.

2. Code examples

1. Note testing

package com.callback2;

public class AsyncCallBack {

    public static void main(String[] args) {
        System.out.println("Start of the main business thread ID:" + Thread.currentThread().getId());
        System.out.println("------------------");

        Son son = new Son();
        Mother mother = new Mother(son);

        mother.notice();
        son.writeHomeWork();

        System.out.println("End of the main business thread ID:" + Thread.currentThread().getId()+"\n");

    }

}

2. Mother

package com.callback2;

public class Mother {
    private Son son;
    public Mother(Son son) {
        this.son = son;
    }

    public void notice() {
        new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println("Notify the mother of the thread ID." + Thread.currentThread().getId());
                cookFood("Bread");
            }
        }).start();
    }

    public void cookFood(String bread) {
        System.out.println("Current cooking thread ID." + Thread.currentThread().getId());
        try {
            System.out.println("Mother Baking" + bread + "...");
            Thread.sleep(3000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        System.out.println("Mother has baked the bread");
        String message = "Ming, come and eat!";

        son.callback(message);

    }

}

3. My son Xiao Ming

package com.callback2;

public class Son {
    private String status = "";

    public void writeHomeWork() {
        System.out.println("Xiaoming writing homework thread ID: " + Thread.currentThread().getId());
        System.err.println("Ming is writing his homework...") ;
        setStatus("Writing homework");
    }


    public void callback(String message) {
        System.out.println("Callback Xiaoming meal thread ID: " + Thread.currentThread().getId());
        System.err.println(message);
        System.err.println("Okay, coming right up!") ;
        System.out.println("Ming started eating!") ;
        setStatus("Eating in progress");
        System.out.println("Xiaoming executing meal thread ID." + Thread.currentThread().getId());
    }

    public String getStatus() {
        return status;
    }
    public void setStatus(String status) {
        this.status = status;
    }
}

4. Implementation results

Business Main Thread Start ID: 1
------------------
Xiaoming writing homework thread ID: 1
Xiaoming writing homework in progress...
Business main thread end ID:1

Notify mother thread ID:12
Currently cooking thread ID:12
Mother baking bread...
Mother baked the bread
Callback to Xiaoming to eat Thread ID: 12
Ming, come and eat!
Okay, coming right up!
Ming starts eating!
Xiaoming executes meal thread ID: 12

5. Result analysis

1) Xiao Ming uses the main thread to do his homework (if he can’t finish it, he doesn’t need to care);

2) Mother uses the new thread to cook [concurrent], mother finishes the meal, executes the callback function, and notifies Xiao Ming to eat;

3) Xiao Ming uses a new thread and starts to eat.


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