multithreading - java.lang.IllegalThreadStateException

Question

I am working with threads. However when I try to start a thread, I get a Exception. In concrete java.lang.IllegalThreadStateException. My code is:

public void readCommand() {
    readThread = new Thread("Thread for reading") {
        public void run() {
            while (running) {
                readBuffer = usbservice.receiveData();
                put(readBuffer);
            }
        }
    };
    readThread.start();
}

What could the problem be?

Answer 1

You are storing the thread in a field. If the method is called in two threads, the readThread.start() can be called twice for the same thread. You need to ensure readCommand is not called multiple times and perhaps not start the readThread again if its already running. e.g. you can synchronized the method and check readThread before you start.