Does the clone method clone overridden methods?

Question

If I clone an instance of the following class, and overridde a method when instancing, will the clone have the overridden method? I haven't found anything regarding this behavior in https://docs.oracle.com/javase/7/docs/api/java/lang/Cloneable.html nor https://docs.oracle.com/javase/7/docs/api/java/lang/Object.html#clone() .

public class ToBeCloned implements Cloneable{
    public int returnInt() {
        return 1;
    }
    public void printTest() {
        System.out.println("returnInt():"+returnInt()+"\nToBeCloned Original");
    }
    @Override
    public ToBeCloned clone() throws CloneNotSupportedException {
        return (ToBeCloned) super.clone();
    }
}

`new ToBeCloned() { @Override...}` is just a short way of creating a subclass. If you clone it, you get another instance of the same subclass, with all the same methods. — khelwood, Aug 24 '20 at 18:33

score 6 · Accepted Answer · answered Aug 24 '20 at 18:34

6

If you do something like

new ToBeCloned() { @Override...}

it is just a short way of creating a subclass and instantiating it. If you clone that instance, you get another instance of the same anonymous subclass, with all the same methods.

answered Aug 24 '20 at 18:34

khelwood

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score 3 · Answer 2 · answered Aug 24 '20 at 18:18

The answer is yes, the clone will contain the overridden methods atleast in javaSE-1.8.

This is illustrated by the following programm and it's output:

public class OverridingMethods {
    public static void main(final String[] args) {
        final ToBeCloned toBeCloned1 = new ToBeCloned();
        final ToBeCloned toBeCloned2 = new ToBeCloned() {
            @Override
            public int returnInt() {
                return 2;
            }
            @Override
            public void printTest() {
                System.out.println("returnInt():"+returnInt()+"\nToBeCloned Overridden");
            }
        };
        ToBeCloned toBeCloned3 = null;
        ToBeCloned toBeCloned4 = null;
        ToBeCloned toBeCloned5 = null;
        try {
            toBeCloned3 = toBeCloned1.clone();
            toBeCloned4 = toBeCloned2.clone();
            toBeCloned5 = toBeCloned4.clone();
        } catch (final CloneNotSupportedException e) {
            e.printStackTrace();
        }
        toBeCloned1.printTest();
        toBeCloned2.printTest();
        toBeCloned3.printTest();
        toBeCloned4.printTest();
        toBeCloned5.printTest();
    }
}

The output of the programm is the following:

returnInt():1
ToBeCloned Original
returnInt():2
ToBeCloned Overridden
returnInt():1
ToBeCloned Original
returnInt():2
ToBeCloned Overridden
returnInt():2
ToBeCloned Overridden

This proofs that the overridden method is kept, even if cloning already cloned instances.

Does the clone method clone overridden methods?

2 Answers2