线程“main”java.lang.IllegalMonitorStateException中的异常

Question

I am working with Thread in Java and i get following error - I don't understand why?!

Code:

import java.util.Random;

public class Test {


    public static void main(String[] args) throws InterruptedException {
     Vlakno sude = new Vlakno("myName"); // Vlakno = thread class

        sude.start();
        sude.wait(); // ERROR IS ON THIS LINE
    }

}

class Vlakno extends Thread {

    private boolean canIRun = true;
    private final String name;

    Vlakno(String name) {
        this.name = name;
    }

    @Override
    public void run() {
        while (canIRun) {
          //  System.out.println("Name: " + name);
        }
    }

    public void mojeStop() {
        System.out.println("Thread "+name +" end...");
        this.canIRun = false;
    }
}

Answer 1

In order to deal with the IllegalMonitorStateException , you must verify that all invocations of the wait method are taking place only when the calling thread owns the appropriate monitor. The most simple solution is to enclose these calls inside synchronized blocks. The synchronization object that shall be invoked in the synchronized statement is the one whose monitor must be acquired.

synchronize (sude) {
  sude.wait();
}

For more information and examples, take a look here .

Answer 2

From the Java Docs of Object.wait

IllegalMonitorStateException - if the current thread is not the owner of the object's monitor.

After the invocation sude.start(); you have two threads running: The current thread and the thread running sude . The current thread is not the owner of the object's monitor.

To ensure that you are the owner of the object's monitor do this:

synchronize (sude) {
  sude.wait();
}