两个线程交替打印（wait/notify）

public class Alternately {
private volatile Boolean preIsA = false;

synchronized void backA() {
	try {
		while (preIsA == true) {
			wait();
		}
		for (int i = 0; i < 5; i++) {
			System.out.println("????????????????????");
		}
		preIsA = true;
		notifyAll();
	} catch (InterruptedException e) {
		e.printStackTrace();
	}
}

synchronized void backB() {
	try {
		while (preIsA == false) {
			wait();
		}
		for (int i = 0; i < 5; i++) {
			System.out.println("????????????????????");
		}
		preIsA = false;
		notifyAll();
	} catch (InterruptedException e) {
		e.printStackTrace();
	}
}

public static void main(String[] args) {
	//Thread A = new Thread(()-> backA());
}

@Test
public void testMethod() {
	for (int i = 0; i < 5; i++) {
		Thread A = new Thread(() -> backA());
		Thread B = new Thread(() -> backB());
		A.start();
		B.start();
	}

}

}