Clone method does not invoke super method JAVA-S0048

Non-final class defines a clone method that does not call super.clone.

Examples

Problematic Code

class T implements Cloneable {

    @Override
    public Object clone() {
        // Does not call super.clone();

        T newObj = new T(...);

        // ...

        return newObj;
    }

}

// ...

class U extends T implements Cloneable {

    @Override
    public Object clone() {
        U newObj = (U)super.clone(); // This is an object of type T! This cast will fail with a ClassCastException.
        // ...

        return newObj;
    }
}

If T is extended by a subclass U, and U calls super.clone, then it is likely that U's clone method will get an object of type T. This will likely fail within the clone method itself when the subclass modifies data. Such code violates the standard contract for clone as stated by the JavaDocs:

By convention, the returned object should be obtained by calling super.clone. If a class and all of its superclasses (except Object) obey this convention, it will be the case that x.clone().getClass() == x.getClass().

Recommended

Always make sure to call super.clone when implementing Cloneable for any class.

class T implements Cloneable {
    @Override
    public Object clone() {
        try {
            T newObj = super.clone();

            // ...

            return newObj;
        } catch (CloneNotSupportedException e) {
            // ...
        }
    }
}

References

• Spotbugs - CN_IDIOM_NO_SUPER_CALL