为什么我们需要在同一对象上进行同步才能使notify（）工作

为什么也

notify

想象一下这种情况：

synchronized(x){        while(x.count < 4) {          x.wait();          //...        }}

现在想象一下

notify

//...println(x.count); // print 3x.count++;if(count == 4)   x.notify()//...

乍一看，整个声音总能按预期工作。
但是，请考虑以下竞争条件：

//Thread1 enters heresynchronized(x){     while(x.count < 4) {         //condition is judged true and thread1 is about to wait          //..but..ohh!! Thread2 is prioritized just now !         //Thread2, acting on notify block side, notices that with its current count incrementation,          //count increases to 4 and therefore a notify is sent....          //but...but x is expected to wait now !!! for nothing maybe indefinitely !       x.wait();       //maybe block here indefinitely waiting for a notify that already occurred!     }}

如果只有我们有办法告诉这一点

notify

主题1：“嗯

notify

x.count <4

线程2：“好吧…为了保持一致，我将在逻辑周围加一个锁，以便 在 您的等待调用释放我们的共享锁 之后
发送通知，这样您将收到此通知，从而可以退出等待状态 ;）”

因此，

notify

= >导致a

notify

wait