Singleton: How to stop create instance via Reflection

Question

I know in Java we can create an instance of a Class by new, clone(), Reflection and by serializing and de-serializing.

I have create a simple class implementing a Singleton.

And I need stop all the way one can create instance of my Class.

public class Singleton implements Serializable{     private static final long serialVersionUID = 3119105548371608200L;     private static final Singleton singleton = new Singleton();     private Singleton() { }     public static Singleton getInstance(){         return singleton;     }     @Override     protected Object clone() throws CloneNotSupportedException {         throw new CloneNotSupportedException("Cloning of this class is not allowed");      }     protected Object readResolve() {         return singleton;     }     //-----> This is my implementation to stop it but Its not working. :(     public Object newInstance() throws InstantiationException {         throw new InstantiationError( "Creating of this object is not allowed." );     } } 

In this Class I have managed to stop the class instance by new, clone() and serialization, But am unable to stop it by Reflection.

My Code for creating the object is

try {     Class<Singleton> singletonClass = (Class<Singleton>) Class.forName("test.singleton.Singleton");     Singleton singletonReflection = singletonClass.newInstance(); } catch (ClassNotFoundException e) {     e.printStackTrace(); } catch (InstantiationException e) {     e.printStackTrace(); } catch (IllegalAccessException e) {     e.printStackTrace(); } 

Answer 1

By adding below check inside your private constructor

private Singleton() {     if( singleton != null ) {         throw new InstantiationError( "Creating of this object is not allowed." );     } } 

Answer 2

Define the singleton like this:

public enum Singleton {     INSTANCE }