Java – how do I test non thread safe classes?

I'm new to threads I'm reading Java concurrency in practice I found the following examples in the book

@NotThreadSafe
public class UnSafeSequence
{
     private int value;
     public int getNext()
     {
         return value++;
     }
}

I want to test this code by writing several threads (or more) that access this class for thread safety

I've tried these, but I'm not sure how to test these examples

class MyThread implemented Runnable
{
    public void run()
    {
        //Should I create a new object for UnSafeSequence here ?
    }
}

Thanks for your help.

Solution

If each thread has its own instance of unsafe sequence, it will not prove the problem What you need to do is create an unsafe sequence instance outside the myThread instance and pass it to the constructor of each myThread

UnSafeSequence unsafe = new UnSafeSequence();
 ...
 new Thread(new MyThread(unsafe)).start();
 new Thread(new MyThread(unsafe)).start();
 ...
 class MyThread implemented Runnable {
       private UnSafeSequence unsafe;
       public MyThread(UnSafeSequence unsafe) {
            this.unsafe = unsafe;
       }
       public void run() {
            ...
            unsafe.getNext();
            ...
       }
 }

While learning threads, be sure to read about executorservice and other excellent classes This is a good tutorial from sun ^ H ^ H ^ H oracle