``++Cloneable++`` is the marker ``++Interface++`` that indicates that ``++clone()++`` may be called on an object. Overriding ``++clone()++`` without implementing ``++Cloneable++`` can be useful if you want to control how subclasses clone themselves, but otherwise, it's probably a mistake. The usual convention for ``++Object.clone()++`` according to Oracle's Javadoc is: . ``++x.clone() != x++`` . ``++x.clone().getClass() == x.getClass()++`` . ``++x.clone().equals(x)++`` Obtaining the object that will be returned by calling ``++super.clone()++`` helps to satisfy those invariants: . ``++super.clone()++`` returns a new object instance . ``++super.clone()++`` returns an object of the same type as the one ``++clone()++`` was called on . ``++Object.clone()++`` performs a shallow copy of the object's state == Noncompliant Code Example ---- class BaseClass { // Noncompliant; should implement Cloneable @Override public Object clone() throws CloneNotSupportedException { // Noncompliant; should return the super.clone() instance return new BaseClass(); } } class DerivedClass extends BaseClass implements Cloneable { /* Does not override clone() */ public void sayHello() { System.out.println("Hello, world!"); } } class Application { public static void main(String[] args) throws Exception { DerivedClass instance = new DerivedClass(); ((DerivedClass) instance.clone()).sayHello(); // Throws a ClassCastException because invariant #2 is violated } } ---- == Compliant Solution ---- class BaseClass implements Cloneable { @Override public Object clone() throws CloneNotSupportedException { // Compliant return super.clone(); } } class DerivedClass extends BaseClass implements Cloneable { /* Does not override clone() */ public void sayHello() { System.out.println("Hello, world!"); } } class Application { public static void main(String[] args) throws Exception { DerivedClass instance = new DerivedClass(); ((DerivedClass) instance.clone()).sayHello(); // Displays "Hello, world!" as expected. Invariant #2 is satisfied } } ---- == See * http://cwe.mitre.org/data/definitions/580.html[MITRE, CWE-580] - clone() Method Without super.clone() * https://wiki.sei.cmu.edu/confluence/x/FjZGBQ[CERT, MET53-J.] - Ensure that the clone() method calls super.clone()