Java循环退出条件

Question

I am writing a network server in java, and I have a tiny problem with it. Let the code do the talking:

import java.io.IOException;
import java.net.ServerSocket;
/**
* Another flavor of the server module.
* According to GOD (also known as Joshua Bloch) this is the proper
* implementation of a singleton (Note: serialization).
* 
* @author estol
*/
public enum EnumSingletonServer implements ServerInterface, Runnable
{
    SERVER;
    private ServerSocket serverSocket = null;
    private boolean Listening         = true;

    @Override
    public void bind() {
        this.bind(DEFAULTPORT);
    }

    @Override
    public void bind(int Port) {
        try {
            this.serverSocket = new ServerSocket(Port);
        } catch (IOException ioe) {
            System.err.printf("Cannot bind to port %d\nAdditional information:\n%s\nExiting\n", Port, ioe.getMessage());
            System.exit(1);
        }
    }

    /**
    * Not that elegant, but does not work with flipping the switch, because
    * the loop (in public void run()) is only running when there is an incoming connection(?).
    * 
    * 
    * FIXME
    */
    @Override
    public void shutdown() {
        // this.Listening = !this.Listening; // FIXME
        System.exit(0);

    }
    /**
    * Accepting connections on the port, we are bound to.
    * The main loop of the server is a bit broken. Does not exit,
    * if we flip the value of this.Listening, but exit on the next incoming
    * connection. This is a problem.
    * 
    * FIXME
    */
    @Override
    public void run() {
        try {
            System.out.printf("Listening on %d\n", this.serverSocket.getLocalPort());
            Thread.currentThread().setName("ServerThread");
            // FIXME
            do {
                new Thread(new ServerWorkerThreads(this.serverSocket.accept(), 3)).start();
            } while (this.Listening);

            this.serverSocket.close();
            System.exit(0);
        } catch (IOException ioe) {
            System.err.printf("Cannot accept on, or close port %d\nAdditional information:\n%s\nExiting\n", this.serverSocket.getLocalPort(), ioe.getMessage());
            System.exit(1);
        }
    }
}

Now, as said in the comments, if I negate/flip/change the value of the variable this.Listening, the loop does not stop, but exits on the next connection.

I did not implement the server in an enumerator at first, I did it with a class, which failed to be a singleton after being serialized, but that executed as I expected it to do so. I tried a while (condition) done, and also the do while(condition) loop.

All help would be appreciated.

Answer 1

In your shutdown method just close the socket instead of setting the variable:

this.serverSocket.close()

This will raise a SocketException on the accept loop and the loop is going to stop.