Polymorphism

AP Computer Science A· difficulty 3/5

public class Animal {
    public String sound() { return "?"; }
}
public class Dog extends Animal {
    public String sound() { return "woof"; }
}
public class Zoo {
    public static String hear(Animal a) { return a.sound(); }
}
// Usage:
System.out.print(Zoo.hear(new Dog()));

What is printed?

A
$Animal$
B
$Compile error$
C
$?$
D
$woof$
check_circle

Explanation

A method that takes Animal can accept any subclass. Dynamic dispatch invokes Dog's sound, returning "woof".

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