Java经典线程问题：三个打印机轮流打字

线程间的通信其实是非常复杂的，这里是一个经典的线程加锁通信的问题。A, B, C三个打印机，每个打印机是一个线程，现在要求写一个程序，让A,B,C轮流打印自己的名字，每个打四次。

public class Printer extends Thread {
    private String msg;
    private Printer next;

    public Printer(String msg) {
        this.msg = msg;
    }

    @Override
    public void run() {

        for (int i = 1; i < 5; i++) {
            synchronized (this) {
                try {
                    this.wait();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println("第" + i + "次：" + this.msg);

                synchronized (this.next) {
                    this.next.notify();
                }
            }
        }
    }

    public static void main(String[] args) {
        Printer A = new Printer("A");
        Printer B = new Printer("B");
        Printer C = new Printer("C");
        A.next = B;
        B.next = C;
        C.next = A;

        A.start();
        B.start();
        C.start();

        try {
            Thread.sleep(100);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        synchronized (A) {

            A.notify();

        }
    }
}