Re: object without reference and gc()

Patricia Shanahan <>
Fri, 08 May 2009 14:47:14 -0700
asit wrote:

Consider the following code

class NewThread implements Runnable {

    Thread t;

    NewThread(String name) {
        t = new Thread(this,name);
        System.out.println("New thread : " + t);

    public void run() {
        try {
            for(int i=0; i<5; i++) {
                System.out.println(this + " : " + i);
        }catch(InterruptedException e) {
            System.out.println("Child interrupted");
        System.out.println("Child thread exiting");

public class MyThread {

    public static void main(String args[] ) {

        Runtime r = Runtime.getRuntime();
        new NewThread("Ok1");
        new NewThread("Ok2");
        new NewThread("Ok3");


        try {
        }catch(InterruptedException e) {
            System.out.println("Main thread interrupted");

        System.out.println("Main thread exiting");


In MyThread class, inside main(), I am creating three objects of
NewThread class without storing there references. Hence when I am
calling garbage collector, all these objects should be killed. But in
reality it is not happening. Can anyone help me ???

"A reachable object is any object that can be accessed in any potential
continuing computation from any live thread."

It's not just accessibility from the main thread that matters. It is
accessibility from *any* live thread, including the ones you started
from the NewThread constructor.

Each NewThread object is "this" for the run method of one of the threads
you started, and therefore accessible from the continuing computation in
that thread until completion of its run method.


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