dev/vala/abstract_class/simple_class.vala

public class Animal : Object {

    public void eat() {
        stdout.printf("*chomp chomp*\n");
    }

    public void say_hello() {
      stdout.printf ("parent hello\n");
    }
}

public class Tiger : Animal {

    public void say_hello_2() {
        stdout.printf("*roar*\n");
    }
}

/*public class Duck : Animal {

    public override void say_hello() {
        stdout.printf("*quack*\n");
    }
}*/