Singleton class

[eleonora]

hey
i have that singleton code in java but how can i check that it have an instance only?

class singleton
{
    private static singleton instance;
    
    private singleton()
    {
    }
    
    public static singleton getInstance()
    {
        if (instance == null){
            instance = new singleton();
        }
        return instance;
    }
}

thanks in advance!

[darkagn]

Yes I think your code will give you exactly one instance of your class.

[eleonora]

yeah but how can i check that indeed have only one instance?

[darkagn]

Put an else statement in your getInstance method that reads

System.out.println("Hey, I'm already created!!");

then try calling getInstance twice. :)

[eleonora]

what do you mean calling the getInstance method twice ???

class singleton
{
    private static singleton instance;
    
    private singleton()
    {
    }
    
    public static singleton getInstance()
    {
        if (instance == null){
            instance = new singleton();
        }else{
            System.out.println("already created");
        }
        return instance;
    }
}

[darkagn]

You will need to call singleton.getInstance() somewhere in your main method to get the instance of the class. Call it twice to see if you can only create one instance.