两个线程都在Java中处于等待状态

Question

我有一个服务器和两个客户端，服务器启动两个线程（ServerHandler），这两个线程都通过相应客户端的Socket TCP连接传递，这些客户端在开始时就连接到服务器。

预期行为：一个ServerHandler线程将消息发送到客户端，而另一个ServerHandler线程等待wait() ...，然后工作线程通知正在休眠的线程并等待...等等。

实际行为：两个ServerHandlers同时等待。

ServerHandler的代码片段（正在运行两个实例）

@Override
public void run() {
    System.out.println(String.format("  --> Server handler: %s is in run method...", serverID));
    while (true) {
        synchronized (this){
            while (!Server.isFinished()) {
                try {
                    System.out.println(String.format("  --> Server handler: %s is waiting...", serverID));
                    wait();
                } catch (InterruptedException e) {
                    Thread.currentThread().interrupt();
                }
            }
            System.out.println(String.format("  --> Server handler: %s is ready to send board...", serverID));
            Server.setFinished(true);
            sendBoard();

            notify();
        }
    }
}

注意：Server类同时启动两个ServerHandler线程。 finished默认设置为false

输出：

CLIENT connected!
<-- I'M Alan I want to play!
--> Server handler 1 instantiated!
CLIENT connected!
<-- I'M Bot I want to play!
--> Server handler 2 instantiated!
HANDLER started...
HANDLER started...
--> Server handler: 1 is in run method...
--> Server handler: 2 is in run method...
--> Server handler: 1 is waiting...
--> Server handler: 2 is waiting...

预期的行为：

CLIENT connected!
<-- I'M Bot I want to play!
--> Server handler 1 instantiated!
CLIENT connected!
<-- I'M Alan I want to play!
--> Server handler 2 instantiated!
HANDLER started...
HANDLER started...
--> Server handler: 1 is in run method...
--> Server handler: 1 is waiting...
--> Server handler: 2 is in run method...
--> Server handler: 2 is ready to send board...
...

谢谢！

Answer 1

您能提供一些有关预期输出的示例吗？

似乎是一个偶然错误的事情是，两个线程都有自己的锁，而不是共享一个锁（请注意static。

没有意义的另一件事是在您已经拥有的锁上调用notify。

private static Object lock = new Object();

public void run() {
    while (true) {
        synchronized (lock) {
            while (!Server.isFinished()) {
                try {
                    lock.wait();
                } catch (InterruptedException e) {
                    Thread.currentThread().interrupt();
                }
            }

            Server.setFinished(true);
            sendBoard();
        }
    }
}