Question regaring Singleton.

This code below is a Singleton which means that only one instance of class Singleton can be created.
But I was able to create tho instances in class
Singleton_Test but the two instances hat the same
content regarding instance variable number which is 4 in bot instances.
Why is it possible to create two instances from class singleton and why do all singleton instances have the content of the last created Singleton instance?
Appreciate your answers.
Thomas

/* Singleton => Ensure a class has only one instance, and provide 
    a global point of access to it. 
   The code below  limits construction to just one instance of
   Singleton class. Consumers of this class only obtain access 
   to the one instance via the getInstance() class method. 
   So by making the only possible constructor private you have to 
   use the public static and final method getInstance() to get an 
   instance of MySingleton. The field myInstance is static so that
   there can only be one instance of it. 
*/
class Singleton {
 int number;
 private static Singleton instance; 
 private Singleton() {super();}  //Private Constructor
 
 public static synchronized Singleton getInstance() {
    if (instance == null) {
        instance = new Singleton();
    } 
    return instance;
 }
 // other stuff below
} 
public class Singleton_Test {
   public static void main(String args[]) {
     Singleton instance = Singleton.getInstance();
       //calls static method getInstance of class Singleton
       //to create the just one instance of that class
     //work with instance....
     instance.number = 3;
     System.out.println(instance.number);
    Singleton instance1 = Singleton.getInstance();
       instance1.number = 4;
     System.out.println(""+instance.number+instance1.number);
   }
}

Result:
C:\Java\EigeneJavaProgramme>java Singleton_Test
3
44

You did not create two instances, only one.
You have two variables which reference the same singleton instance.
You can test that by checking that instance==instance1.
The reason they both have the same contents is because they are the same object.

...but if you really did want to (kinda) subvert the notion of static in Java, take a look at http://www.javageeks.com/Papers/JavaStatics/JavaStatics.pdf