package beginner;

import static com.sandwich.koan.constant.KoanConstants.__;

import static com.sandwich.util.Assert.assertEquals;

import java.util.Collection;

import java.util.Collections;

import java.util.List;

import com.sandwich.koan.Koan;

public class AboutInheritance {

class Parent {

public String doStuff() { return "parent"; }

}

class Child extends Parent {

public String doStuff() { return "child"; }

public String doStuff(String s) { return s; }

}

@Koan

public void differenceBetweenOverloadingAndOverriding() {

assertEquals(new Parent().doStuff(), __);

assertEquals(new Child().doStuff(), __);

assertEquals(new Child().doStuff("oh no"), __);

}

abstract class ParentTwo {

abstract public Collection<?> doStuff();

}

class ChildTwo extends ParentTwo {

public Collection<?> doStuff() { return Collections.emptyList(); };

}

@Koan

public void overriddenMethodsMayReturnSubtype() {

// What do you need to change in order to get rid of the type cast?

// Why does this work?

List<?> list = (List<?>) new ChildTwo().doStuff();

assertEquals(list instanceof List, __);

}

}