Java 8 | Default methods for interface

Java 8 enables us to add non-abstract method implementations to interfaces by utilizing the default keyword. This feature is also known as Extension Methods.

interface Formula {

    double calculate(int a);

    default double sqrt(int a) {

        return Math.sqrt(a);

    }

}

Formula formula = new Formula() {

    @Override

    public double calculate(int a) {

        return sqrt(a * 100);

    }

};

formula.calculate(100);     // 100.0

formula.sqrt(16);           // 4.0

}