Thread Local only initializing to Zero

Question

I was implementing a Thread Local example using following code, I thought I'd be getting random numbers in the output but when the threadLocal.get() method is called I get a zero for all threads n output, am I missing something here. Here is my code and the output, will deeply appreciate the help. Thanks in advance.

package concurrency;

public class ThreadLocalExample {

    public static void main(String[] args) throws InterruptedException {
        SubLocalClass subLocalClass = new SubLocalClass();
        for(int i=0;i<10;i++) {
             Thread thread = new Thread(subLocalClass);
             thread.start();
             thread.join();

        }
    }

}

class SubLocalClass implements Runnable{
    private ThreadLocal<Integer> threadLocal =  new ThreadLocal<Integer>() {
        protected Integer initialValue() {
            return 1000;

        }
    };

    @Override
    public void run() {
        threadLocal.set((int) Math.random());
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println(Thread.currentThread().getId()+" "+
        Thread.currentThread().getName()+" "+threadLocal.get());
    }

}

And the output that I am getting is this

12 Thread-0 0
13 Thread-1 0
14 Thread-2 0
15 Thread-3 0
16 Thread-4 0
17 Thread-5 0
18 Thread-6 0
19 Thread-7 0
20 Thread-8 0
21 Thread-9 0

why 0 for threadLocal.get() for all the threads, shouldn't it be publishing random numbers?

Thanks for your help on this.

Answer 1

You set the thread local to zero:

threadLocal.set((int) Math.random());

Because Math.random() returns a double between 0 and 1, when you cast it to an int it will yield 0.