Creating References Using Inheritance Hierarchies

AP Computer Science A· difficulty 3/5

public class A { public String s() { return "A"; } }
public class B extends A { public String s() { return "B"; } }
public class C extends A { public String s() { return "C"; } }
A[] arr = { new A(), new B(), new C() };
for (A x : arr) System.out.print(x.s());

What is printed?

A
$BCA$
B
$Compile-time error$
C
$AAA$
D
$ABC$
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Explanation

Each element invokes its actual runtime type's method via dynamic dispatch.

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