Given: class A { public void mA() {System.out.println("mA");}} class B extends A {public void mB() {System.out.println("mB");}} class C extends B {public void mC() {System.out.println("mC");}}…

The correct answer is E. mA. Option E (mA) is listed as correct, but this answer key contains an error - the program actually prints mB. Since C extends B, the runtime type of cObj (which is C) satisfies instanceof B, making the condition true; the if branch executes and v.mB() prints "mB", never reaching…

Java Object-Oriented Approach

Question

Given:
class A { public void mA() {System.out.println("mA");}}
class B extends A {public void mB() {System.out.println("mB");}}
class C extends B {public void mC() {System.out.println("mC");}}
public class App {
public static void main(String[] args) {
A bObj = new B();
A cObj = new C();
if (cObj instanceof B v) {
v.mB();
} else {
cObj.mA();
}
}
}
What is the result?

Options

How the community answered

(49 responses)

A
2% (1)
B
2% (1)
C
6% (3)
D
12% (6)
E
78% (38)

Explanation

Option E (mA) is listed as correct, but this answer key contains an error - the program actually prints mB. Since C extends B, the runtime type of cObj (which is C) satisfies instanceof B, making the condition true; the if branch executes and v.mB() prints "mB", never reaching the else branch that would call cObj.mA().

Why each distractor fails:

A/C (Mb): These appear to be the same as the real answer ("mB"), suggesting a case-sensitivity formatting error in the choices; the actual output "mB" comes from System.out.println("mB").
B (MC/mC): mC() is never called; nothing in the code invokes it.
D (MA/mA): This would only print if the instanceof B check were false - but since C is a subtype of B, it is always true, so the else branch is unreachable.

Memory tip: For instanceof with pattern matching, remember the chain: if C extends B, then every C is also a B (and also an A). Always trace the full inheritance chain before evaluating the condition - if the runtime type is a descendant of the tested type, the check passes.

Note to exam takers: Verify the answer key with your instructor - based on Java semantics, the correct output should be "mB", not "mA".

Topics

#Pattern Matching#instanceof#Inheritance#Polymorphism

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