线程---同步（synchronized）

public class Test {
	public static void main(String[] args) {
		Controller controller = new Controller();
		new A(controller).start();;
		new B(controller).start();;
		new C(controller).start();;
	}
}

public class Controller {

	private int f=0;
	
	public synchronized void printA(){
		if(f==0){
			System.out.println("A");
			f=1;
			notifyAll();
		}
		try {
			wait();
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
	}
	
	public synchronized void printB(){
		if(f==1){
			System.out.println("B");
			f=2;
			notifyAll();
		}
		try {
			wait();
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
	}
	
	public synchronized void printC(){
		if(f==2){
			System.out.println("C");
			f=0;
			notifyAll();
		}
		try {
			wait();
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
	}
	
}

public class A extends Thread{

	private Controller controller;
	
	A(Controller controller){
		this.controller = controller;
	}
	
	@Override
	public synchronized void run() {
		for (int i = 0; i 

public class B extends Thread{

	private Controller controller;
	
	B(Controller controller){
		this.controller = controller;
	}
	
	@Override
	public synchronized void run() {
		for (int i = 0; i 

public class C extends Thread{

	private Controller controller;
	
	C(Controller controller){
		this.controller = controller;
	}
	
	@Override
	public void run() {
		for (int i = 0; i