Java class inheritance, private fields accessible in subclass, why?

Question

I have code very much like the following.

package my.pkg;

public abstract class X {
    private CapableField field;

    public abstract void doSomething();

    public X(CapableField fieldValue) {
        this.field = fieldValue;
    }
}

And:

package my.pkg.sub;

public class Y extends my.pkg.X {
    public void doSomething() {
        this.field.doSomething();
    }
}

Why is this even legal code in Java? I thought "private" meant that the field will not be directly accessible in subclasses, and that this was a fairly basic tenet of class inheritance. Making X concrete instead of abstract changes nothing.

What do I do if I specifically want a field, or member function, to be accessible only inside the class where it is defined, and not in some random subclass of the defining class?

Can't be. You should have a compilation error! Are you sure that pasted code is what you actually compiled? — Lukas Eder
– Lukas Eder, Commented Feb 21, 2011 at 10:55
As others already noted, this is not legal in Java. private indeed means what you thought it means. What compiler / IDE you are using? — Péter Török
– Péter Török, Commented Feb 21, 2011 at 10:56

BalusC · Accepted Answer · 2011-02-21 10:56:29Z

3

This is not true. Most likely you've actually definied Y as an inner class. This way the private fields of the outer class are indeed visible like that.

answered Feb 21, 2011 at 10:56

BalusC

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1 Comment

user Over a year ago

No, they are separate classes with an inheritance relationship. However, as noted, that was not my problem.

adarshr · Accepted Answer · 2011-02-21 10:58:57Z

2

Doesn't compile for me too! I suspect your Java implementation.

answered Feb 21, 2011 at 10:58

adarshr

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Comments

Sergey Vedernikov · Accepted Answer · 2011-02-21 10:57:44Z

1

This is impossible. May be you missed something when you explain your question.

answered Feb 21, 2011 at 10:57

Sergey Vedernikov

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1 Comment

user Over a year ago

Indeed. Buried deep in the actual code for Y was private CapableField field;. Talk about stupid; when I took that out I got exactly the compilation errors I was expecting. PEBKAC, obviously.

GuruKulki · Accepted Answer · 2011-02-21 10:59:01Z

0

private members are not visible in inheritance except in inner class scope. If you want them to be accessed by the subclass then declare them as protected. or use setters and getters.

and in your code you used package keyword in your package declaration which is not allowed and gives compilation error.

answered Feb 21, 2011 at 10:59

GuruKulki

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Comments

Feras Odeh · Accepted Answer · 2011-02-21 12:19:50Z

0

Make sure that your classes in two different files. for example X.java and Y.java and y not an inner class

answered Feb 21, 2011 at 12:19

Feras Odeh

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