方法一：通過共享物件鎖加上可見變數來實現。

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();
		}
	}

}
 

可以看到執行緒的啟動按順序執行了。共享物件鎖，可以保證每個方法只能同時有一個執行緒進入，配合wait和notifyall方法，可以啟動或者喚醒執行緒。

     方法二：通過主執行緒Join()

class T11 extends Thread {
    public void run() {
        System.out.println("in T1");
    }
}

class T22 extends Thread {
    public void run() {
        System.out.println("in T2");
    }
}

class T33 extends Thread {
    public void run() {
        System.out.println("in T3");
    }
}

public class Test2 {
    public static void main(String[] args) throws InterruptedException {
        T11 t1 = new T11();
        T22 t2 = new T22();
        T33 t3 = new T33();
        t1.start();
        t1.join();
        t2.start();
        t2.join();
        t3.start();
    }
}

   方法三：通過執行緒執行時Join()

class T1 extends Thread {
    public void run(){
        Random random = new Random();
        try {
            Thread.sleep(random.nextInt(1000));
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println("in T1");
    }
}

class T2 extends Thread{
    private Thread thread;
    public T2(Thread thread) {
        this.thread = thread;
    }

    public void run(){
        try {
            thread.join();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println("in T2");
    }
}

class T3 extends Thread{
    private Thread thread;
    public T3(Thread thread) {
        this.thread = thread;
    }

    public void run(){
        try {
            thread.join();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println("in T3");
    }
}

public class Test {
    public static void main(String[] args) throws InterruptedException {
        T1 t1 = new T1();
        T2 t2 = new T2(t1);
        T3 t3 = new T3(t2);
        t2.start();
        t1.start();
        t3.start();
    }
}