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Too Strong Magic
Too Strong Magic

Reputation: 136

Invoking main() method from parent class

There is a code:

class Test1{
    public static void main(String[] args){     
        System.out.println("Test1");
    }
}

class Test2 extends Test1{
}

When I try to execute java Test1 I'm getting, of course, this:

Test1

But, when I try to execute java Test2 I'm still getting:

Test1

Why? In class Test2 doesn't exist main() method. And static methods don't inherited. If I'll add main() in Test2 (with string "Test2" instead of "Test1") I'll get:

Test2

I understand why I'm getting Test2 in this example. But don't understand why I'm getting Test1 if main() doesn't exist in class Test2.

Upvotes: 3

Views: 314

Answers (2)

Pshemo
Pshemo

Reputation: 124275

And static methods don't inherited.

Static methods are inherited. Take a look at jls-8.4.8 Inheritance, Overriding, and Hiding

A class C inherits from its direct superclass and direct superinterfaces all abstract and non-abstract methods of the superclass and superinterfaces that are public, protected, or declared with default access in the same package as C, and are neither overridden (§8.4.8.1) nor hidden (§8.4.8.2) by a declaration in the class.

There is no information about not inheriting static methods, which is why you can run main declared in Test1 via Test2 class (it was inherited).

Also from jls-8.4.8.2 Hiding (by Class Methods)

If a class declares a static method m, then the declaration m is said to hide any method m', where the signature of m is a subsignature (§8.4.2) of the signature of m', in the superclasses and superinterfaces of the class that would otherwise be accessible to code in the class.

So when you created new main method in Test2 class you hidden (not overridden) Test1.main method which is why you saw as output 

Test2

Upvotes: 3

Mike Thomsen
Mike Thomsen

Reputation: 37526

Static methods do in fact get inherited. That's what's happening here. Ex. this works just fine:

class Base {
    public static void saySomething() {
        System.out.println("Hi!");
    }
}

class Extended extends Base {
    public static void main(String[] args) {
        saySomething();
    }
}

Upvotes: 2

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