java 保證線程順序的幾種方式

 方法一：通過共享對象鎖加上可見變量來實現。

public class MyService {

    private volatile int orderNum = 1;

    public synchronized void methodA() {
        try {
            while (orderNum != 1) {
                wait();
            }
            for (int i = 0; i < 2; i++) {
                System.out.println("AAAAA");
            }
            orderNum = 2;
            notifyAll();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    public synchronized void methodB() {
        try {
            while (orderNum != 2) {
                wait();
            }
            for (int i = 0; i < 2; i++) {
                System.out.println("BBBBB");
            }
            orderNum = 3;
            notifyAll();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    public synchronized void methodC() {
        try {
            while (orderNum != 3) {
                wait();
            }
            for (int i = 0; i < 2; i++) {
                System.out.println("CCCCC");
            }
            orderNum = 1;
            notifyAll();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

import service.MyService;
public class ThreadAA extends Thread {

    private MyService dbtools;

    public ThreadAA(MyService dbtools) {
        super();
        this.dbtools = dbtools;
    }

    @Override
    public void run() {
        dbtools.methodA();
    }

}

import service.MyService;
public class ThreadBB extends Thread {

    private MyService dbtools;

    public ThreadBB(MyService dbtools) {
        super();
        this.dbtools = dbtools;
    }

    @Override
    public void run() {
        dbtools.methodB();
    }

}

import service.MyService;
public class ThreadCC extends Thread {

    private MyService dbtools;

    public ThreadCC(MyService dbtools) {
        this.dbtools = dbtools;
    }

    @Override
    public void run() {
        dbtools.methodC();
    }

}

import extthread.ThreadCC;
import service.MyService;
import extthread.ThreadAA;
import extthread.ThreadBB;

public class Run {

    public static void main(String[] args) {
        MyService myService = new MyService();
        for (int i = 0; i < 2; i++) {
            ThreadBB output = new ThreadBB(myService);
            output.start();
            ThreadAA input = new ThreadAA(myService);
            input.start();
            ThreadCC threadCC = new ThreadCC(myService);
            threadCC.start();
        }
    }

}

執行結果：