Given: public class A { private boolean checkValue(int val) { return true; } } and public class B extends A { public int modifyVal(int val) { if (checkValue(val)) { return val; } else { return 0; }…

The correct answer is B. Fails to compile. Option B is correct because checkValue is declared private in class A, meaning it is invisible outside of class A - including to subclasses. When class B calls checkValue(val), the Java compiler cannot resolve that method within B's scope and raises a compile-time error. E (10)…

Java Object-Oriented Approach

Question

Given:
public class A {
private boolean checkValue(int val) {
return true;
}
}
and
public class B extends A {
public int modifyVal(int val) {
if (checkValue(val)) {
return val;
} else {
return 0;
}
}
}
and
public static void main(String[] args) {
B b = new B();
System.out.println(b.modifyVal(10));
}
What is the result?

Options

ANothing
BFails to compile.
C0
DA java.lang.IllegalArgumentException is thrown.
E10

How the community answered

(26 responses)

A
15% (4)
B
73% (19)
D
4% (1)
E
8% (2)

Explanation

Option B is correct because checkValue is declared private in class A, meaning it is invisible outside of class A - including to subclasses. When class B calls checkValue(val), the Java compiler cannot resolve that method within B's scope and raises a compile-time error. E (10) is wrong because even though checkValue always returns true, B never gets to call it - the code never compiles. C (0) is wrong for the same reason; return 0 requires the else branch to execute at runtime, which is impossible if compilation fails. A and D are wrong because both require the program to actually run - no output and no exception can be produced when the compiler rejects the code before execution.

Memory tip: Think of private as a vault that only the declaring class holds the key to - not even its own children can inherit it. When you see a subclass calling a private method from a parent, immediately flag it as a compile error.

Topics

#Access modifiers#Inheritance#Private methods#Compilation

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