class Parent {
    protected final String foo;

    public Parent(String foo) {
        init();
        this.foo = foo;
    }
    protected void init() {
        
    }
}

public class Main extends Parent {

    public Main(String foo) {
        super(foo);
    }

    @Override
    protected void init() {
        System.out.println(this.foo.toLowerCase());
    }

    public static void main(String[] args) {
        new Main("a");
    }
}