abc交替打印

class SyncWaitNotify {
	 private int flag;
	 private int loopNumber;
	 public SyncWaitNotify(int flag, int loopNumber) {
		 this.flag = flag;
		 this.loopNumber = loopNumber;
	 }
	 public void print(int waitFlag, int nextFlag, String str) {
		 for (int i = 0; i < loopNumber; i++) {
			 synchronized (this) {
				 while (this.flag != waitFlag) {
					 try {
						 this.wait();
					 } catch (InterruptedException e) {
						 e.printStackTrace();
					 }
				 }
				 System.out.print(str);
				 flag = nextFlag;
				 this.notifyAll();
			 }
		 }
	 }
}

//main
SyncWaitNotify syncWaitNotify = new SyncWaitNotify(1, 5);
new Thread(() -> {
	 syncWaitNotify.print(1, 2, "a");
}).start();
new Thread(() -> {
	 syncWaitNotify.print(2, 3, "b");
}).start();
new Thread(() -> {
	 syncWaitNotify.print(3, 1, "c");
}).start();