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Concept

The final Keyword

The three uses of Java's final keyword — final variables, methods, and classes.

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There are three uses of the final keyword:

  1. Final variable
  2. Final method
  3. Final class

Final variable

A constant — its value is fixed and cannot be modified.

class My {
    final int MIN = 1; // can be initialized and defined at once
    final int NORMAL;
    final int MAX;


    static {
        NORMAL = 5; // can be initialized inside a static block
    }
    My() {
        MAX = 10; // can be initialized inside a constructor
    }
}

Final method

These methods cannot be overridden.

class Super {
    final void meth1() {
        System.out.println("Hello");
    }
}


class Sub extends Super {
    // void meth1() {} // wrong — final methods cannot be overridden
    void meth2() {
        System.out.println("Bye");
    }
}

Final class

These classes don’t support inheritance — they cannot be extended, but you can still create objects of them.

final class Super {
    // some code here
}


// class Sub extends Super { } // wrong — final classes cannot be extended