Overriding interface's variable?

Question

As I read from various Java book and tutorials, variables declared in a interface are constants and can\'t be overridden.

I made a simple code to test it

<         


        

Answer 1

Default signature for any variable in an interface is

public static final ...

So you cannot override it anyhow.

Answer 2

The variable you declared in that interface is not visible to the class that implemented it.

If you declare a variable in an static and final, i.e. a constant, THEN it is visible to implementors.

Answer 3

You did not override the variable, you shadowed it with a brand-new instance variable declared in a more specific scope. This is the variable printed in your printx method.

Answer 4

It is not overridden, but shadowed, with additional confusion because the constant in the interface is also static.

Try this:

A_INTERFACE o = new A_CLASS();
System.out.println(o.var);

You should get a compile-time warning about accessing a static field in a non-static way.

And now this

A_CLASS o = new A_CLASS();
System.out.println(o.var);
System.out.println(A_INTERFACE.var);  // bad name, btw since it is const