Polymorphism

AP Computer Science A· difficulty 2/5

public class Animal {
    public String sound() { return "generic"; }
}
public class Dog extends Animal {
    public String sound() { return "Woof"; }
}
Animal a = new Dog();
System.out.println(a.sound());

What is printed?

A
$Woof$
check_circle
B
$generic$
C
$Compile-time error$
D
$Runtime error$

Explanation

Java uses dynamic dispatch: even though <code> a </code> is declared as <code> Animal </code>, the actual object is a <code> Dog </code>, so <code> Dog.sound() </code> is invoked at runtime.

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