Should I use a class name when referencing a static field in that class?

If I have a class with a static field such as:

public class Foo {
    public static int bar;
}

...And I want to reference this field within its declared class. I am aware that both:

public class Foo {
    public static int bar;
    public static int getBar() {
        return bar;
    }
}

And:

public class Foo {
    public static int bar;
    public static int getBar() {
        return Foo.bar;
    }
}

work. Is there any preference or convention between whether or not to include the class name like that? Any help is appreciated.

Actually, its totally opinion based. You should do whatever method you prefer. Both are equally granted. But I would like to add one point, if you are using getter/setter, then declare the static variable private:

public class Foo {
    private static int bar;
    public static int getBar() {
        return bar;
    }
    public static int setBar(int _bar) {
        bar = _bar;
    }
}

And as the both getter and setter methods are static, it ensures, they both definitely work with only static variables of Foo class. This solves readability problem too.

I agree with whatever being mentioned in the comments. Apart from this, I keep readability of the code in mind and then decide. Following code fragment gives an idea on the same:

public class Engine {
    private static boolean isOn = false;
    public static void doWork1() {
        if (isOn) { // check if engine is on
            // do some work
        }
    }
    public static void doWork2() {
        if (Engine.isOn) {
            // do some work
        }
    }
    ...
}

You can see that doWork2() method by using the class name increased the code readability even without adding any comment to the code.