Quiz J2-1

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Question 1

What is the output of the below program?

class A {
    public String toString(){
        return "A";
    }
}

class B extends A{
    public String toString() {
        return "B";
    }
}

class C extends A {
    public String toString() {
        return super.toString();
    }
}

class D extends C {
    public String toString() {
        return super.toString();
    }
}

public class tmp{
    public static void main(final String args[]) {
        D d = new D();
        System.out.println(d.toString());
    }
}

Question 2

Consider the below program. What is the output?

class A {
    public String toString(){
        return "A";
    }
    
    public String fancyToString() {
        return "~~A~~";
    }
}

class B extends A{
    public String toString() {
        A letterA = this;
        return letterA.fancyToString();
    }
    public String fancyToString(){
        return "~~B~~";
    }
}

public class LetterPrinter{
    public static void main(final String args[]) {
        B letterB = new B();
        System.out.print(letterB.toString()+ " ");
        
        A letterA = letterB;
        System.out.println(letterA.toString());
    }
}

Question 3

What if class B’ did not implement a toString method, like in below?

class B extends A{
    public String fancyToString(){
        return "~~B~~";
    }
}

Question 4

What is the output of the program below?

class A{
    public String toString(){
        return "A";
    }
}
class B extends A{
    public String toString(){
        return "B";
    }
}
public class PolymorphicOverload{
    public void foo(B letterB1, B letterB2) {
        // 2
        System.out.println("foo2: " + letterB1 + " " + letterB2);
    }

    public void foo(A letterA1, A letterA2){
        //1
        System.out.println("foo1: " + letterA1 + " " + letterA2);
    }
    public static void main(String args[]){
        PolymorphicOverload f = new PolymorphicOverload();
        B letterB = new B();
        A letterA = (A) new B();
        f.foo(letterB, letterA);
    }
}