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public class ABC_Synch {
public static class ThreadPrinter implements Runnable {
private String name;
private Object prev;
private Object self;
private ThreadPrinter(String name, Object prev, Object self) {
this.name = name;
this.prev = prev;
this.self = self;
}
@Override
public void run() {
int count = 10;
while (count > 0) {// 多线程并发，不能用if，必须使用whil循环
synchronized (prev) { // 先获取 prev 锁
synchronized (self) {// 再获取 self 锁
System.out.print(name);
//打印
count--;
self.notifyAll();
// 唤醒其他线程竞争self锁，注意此时self锁并未立即释放。
}
//此时执行完self的同步块，这时self锁才释放。
try {
prev.wait();
// 立即释放 prev锁，当前线程休眠，等待唤醒
/**
* JVM会在wait()对象锁的线程中随机选取一线程，赋予其对象锁，唤醒线程，继续执行。
*/
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
}
public static void main(String[] args) throws Exception {
Object a = new Object();
Object b = new Object();
Object c = new Object();
ThreadPrinter pa = new ThreadPrinter("A", c, a);
ThreadPrinter pb = new ThreadPrinter("B", a, b);
ThreadPrinter pc = new ThreadPrinter("C", b, c);
Thread thread = new Thread(pa);
new Thread(pa).start();
Thread.sleep(10);
//保证初始ABC的启动顺序
new Thread(pb).start();
Thread.sleep(10);
new Thread(pc).start();
Thread.sleep(10);
}
}
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