Question

What is the answer?
Polymorphism and dynamic binding (4 points total; 1 point each part)
Consider the following three classes:
public class Gee {
public String first() {
return "fee";
}
public String second() {
return "fi";
}
}
public class Tee extends Yee {
public String first() {
return "fo";
}
}
public class Yee extends Gee {
public String second() {
return "fum" + first();
}
public String third() {
return "from";
}
}

Assume that you have the following variable declarations, all of which are valid:
Gee g = new Yee();
Yee y1 = new Yee();
Yee y2 = new Tee();
Tee t = new Tee();

Consider the following statements. If a given statement would compile, state the output that it would produce when it is executed. If a given statement would not compile, explain why.

System.out.println(g.first() + " " + g.second() + " " + g.third());
System.out.println(y1.first() + " " + y1.second() + " " + y1.third());
System.out.println(y2.first() + " " + y2.second() + " " + y2.third());
System.out.println(t.first() + " " + t.second() + " " + t.third());

Answer 1

1. System.out.println(g.first() + " " + g.second() + " " + g.third());
// this statement is not valid because the method third() is undefined for the type Gee

2. System.out.println(y1.first() + " " + y1.second() + " " + y1.third());
//result is “fo fumfo from”

3. System.out.println(y2.first() + " " + y2.second() + " " + y2.third());
//result is “fee fumfee from”

4. System.out.println(t.first() + " " + t.second() + " " + t.third());
//result is “fo fumfo from”