Why there are suddenly 3 Threads in my Java program?

Question

as the title implies I do not know how there could be three threads in my program?

My suggestion is:

(1) main-Thread

(2) EDT (because of JButton)

(3) ????

Here is my Code (it is very simple):

package newProject;

import javax.swing.JButton;

public class MyExample {

    public static void main(String[] args) {

        System.out.println(Thread.activeCount() + " " + Thread.currentThread());
        MyThread myExample = new MyThread();
        System.out.println(Thread.activeCount() + " " + Thread.currentThread());
    }

}

class MyThread {

    JButton button=new JButton();

                    public MyThread() {

                    }
}

Answer 1

The name of a thread is always helpful. You can list all threads by name via:

import java.util.*;

public class ListThreads {

     public static void main(String []args){
        Set<Thread> threadSet = Thread.getAllStackTraces().keySet();
        for (Thread t : threadSet) {
            System.out.println (t.getName());
        }
     }
}

For me it lists:

• Finalizer
• Signal Dispatcher
• main
• Reference Handler

EDIT: The threadSet line was taken from here: Get a List of all Threads currently running in Java