Java multithreads - Identify the error in the code

Question

So this code was given in an exam and the question was what's wrong with it. It's meant to create new objects of type SomeClass but only if they were not created earlier.

class Foo {
    private SomeClass x = null;
    public synchronized SomeClass getX() {
        if (x == null)
            x = new SomeClass();
        return x;
    }
}

My guess is that x and getX should be declared static since otherwise there may be multiple copies of x. Is that correct? if so is that the only problem in the code?

There's nothing inherently wrong with this class (except the missing closing brace, the bad naming and lack of documentation). It could not do what it's supposed to do, but since it has zero documentation, we can't know what it's supposed to do. — JB Nizet
– JB Nizet, Commented Apr 7, 2013 at 14:44

Frank · Accepted Answer · 2013-04-07 14:55:19Z

1

You are trying to build a singleton factory method:

public class Foo {
    private static SomeClass x = null;
    public static synchronized SomeClass getSomeClass() {
        if (x == null)
            x = new SomeClass();
        return x;
    }
}

Note that if you really need this, you should also make SomeClass an inner class of Foo, and make the constructor of SomeClass private.

answered Apr 7, 2013 at 14:55

Frank

15.7k6 gold badges38 silver badges50 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Java multithreads - Identify the error in the code

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related