In testing work fines, but won't pass the validator

Question about the task

Under discussion

Hi Everyone, I came up with this solution here:

@Override
public Object clone() throws CloneNotSupportedException {
        if(this instanceof B && !(this instanceof C)) return new CloneNotSupportedException();
    return super.clone();
}

During testing it works fine but it won't pass the validator. I wonder if there is a test case in which it won't work? Is this solution just wrong? Or maybe it's too specific to this particular case and a more general solution would be better? Any help would be greatly appreciated to understand why it doesn't work. Thanks in advanced!

Allow cloning of the A class
Prevent cloning of the B class
Allow cloning of the C class
Don't forget about the equals and hashCode methods!

Requirements:

The A class should support the Cloneable interface.
The B class must be a descendant of the A class.
The B class's declaration should not explicitly state "implements Cloneable".
The B class's clone method must be overridden in such a way that an attempt to clone a B object will generate a CloneNotSupportedException.
The C class must be a descendant of the B class.
C objects must be cloned successfully.

package com.codegym.task.task21.task2109; /* Prevent cloning */ public class Solution { public static class A implements Cloneable { private int i; private int j; public A(int i, int j) { this.i = i; this.j = j; } public int getI() { return i; } public int getJ() { return j; } } public static class B extends A { private String name; public B(int i, int j, String name) { super(i, j); this.name = name; } public String getName() { return name; } @Override public Object clone() throws CloneNotSupportedException { if(this instanceof B && !(this instanceof C)) return new CloneNotSupportedException(); return super.clone(); } } public static class C extends B implements Cloneable { public C(int i, int j, String name) { super(i, j, name); } @Override public Object clone() throws CloneNotSupportedException { return super.clone(); } } public static void main(String[] args) throws CloneNotSupportedException { B class1 = new B(20, 35, "Dog"); B class2 = (B) class1.clone(); C class3 = new C(25, 40, "Happy"); C class4 = (C) class3.clone(); System.out.println(class3 + " " + class4); } }

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Brandon Waites

Level 26 , Cincinnati, United States

31 May 2023, 15:59

I wonder if the validator is looking at line 43 and assuming it can reach that point. If so, then we automatically fail the validation requirement to prevent cloning of the B class. If not, then we have unreachable code. My initial thought is that line 43 is superfluous, and you may or may not need to revise line 42 to prevent cloning of the B class at all costs. I hope this helps.