How do I enable and restrict cloning in Java?

How can we stop cloning in Java?

Prevent Singleton Pattern From Cloning

To overcome the above issue, we need to implement/override the clone() method and throw an exception CloneNotSupportedException from the clone method. If anyone tries to create a clone object of Singleton , it will throw an exception, as shown in the below code.

How can we stop cloning?

Avoid implementing clone . If you need to extend a superclass that implements clone , then your subclass must implement clone as well. The quickest solution is for your subclass to simply throw an exception.

How can we prevent clone of singleton object in Java?

Overcome Cloning issue:- To overcome this issue, override clone() method and throw an exception from clone method that is CloneNotSupportedException. Now whenever user will try to create clone of singleton object, it will throw exception and hence our class remains singleton.

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Why clone method is protected in Java?

clone is protected because it is something that ought to be overridden so that it is specific to the current class. While it would be possible to create a public clone method that would clone any object at all this would not be as good as a method written specifically for the class that needs it.

What happens if I clone singleton object?

What is Object Cloning? The object cloning is a way to create exact copy of an object. So if somebody will clone our singleton instance, it will create another copy of the Singleton instance which violates principle of Singleton Design Pattern.

How can we prevent singleton from reflection using enum?

How to prevent Reflection API from breaking Singleton

  1. private ReflectionSingleton() { if (instance != null ) {
  2. throw new IllegalStateException( “instance already created.” ); }
  3. System.out.println( “Singleton instance is being created.” ); }

Can we clone final class in Java?

You don’t implement the clone() method in the abstract class, only in the concrete sub-classes.

What is deep cloning and shallow cloning in Java?

Summary. In shallow copy, only fields of primitive data type are copied while the objects references are not copied. Deep copy involves the copy of primitive data type as well as object references.

What is cloneable interface in Java?

Cloneable interface is a marker interface. It was introduced in JDK 1.0. There is a method clone() in the Object class. Cloneable interface is implemented by a class to make Object. clone() method valid thereby making field-for-field copy.

What is double checked locking in singleton?

In double-checked locking, code checks for an existing instance of Singleton class twice with and without locking to make sure that only one instance of singleton gets created.

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How do you make a singleton thread safe in Java?

Thread Safe Singleton in Java

  1. Create the private constructor to avoid any new object creation with new operator.
  2. Declare a private static instance of the same class.
  3. Provide a public static method that will return the singleton class instance variable.

What is the best way to create Singleton class in Java?

1. Eager initialization: In eager initialization, the instance of Singleton Class is created at the time of class loading, this is the easiest method to create a Singleton class. By making the constructor as private you are not allowing other class to create a new instance of the class you want to create the Singleton.

Can we override clone method in Java?

Every language which supports cloning of objects has its own rules and so does java. In java, if a class needs to support cloning it has to do following things: You must implement Cloneable interface. You must override clone() method from Object class.

Why do we need to override clone method?

Because, for a class to be cloned, you need to implement the Cloneable interface. And then your class uses the clone method of Object class instead. Because, Cloneable interface doesn’t exactly have any method for cloning . It would be a better option to use Copy Constructor instead.

Why clone method is not visible?

When a method is protected, it can only be accessed by the class itself, subclasses of the class, or classes in the same package as the class. Your class StringWrap cannot access the clone() method of class Nil, because class StringWrap is not a subclass of class Nil.

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