Whats wrong in the code snippet below ?

[lifeisgreat20009]

(This is not a trick question, there is a potential real problem in using this code)

class Singleton{
         public static Singleton Instance() {
                  if (_instance == null)
                       _instance = new Singleton();
                  return _instance;
         }
         protected Singleton() {}
         private static Singleton _instance = null;
}

[JosAH]

Multiple Threads, each trying to obtain your 'singleton'. Synchronize that static method.

kind regards,

Jos

[dmjpro]

@lifeisgreat20009
Actually no syntactical error with your code. Then how did you say that it's error?

[JosAH]

@dmjpro
It helps if you read the entire thread first before you hit the 'Submit Reply' button.

kind regards,

Jos

[dmjpro]

@Joash
Sorry!! :(

If i write the code like this...

public SingleTone{
private static _instance = new SingleTone();
public static getInstance(){
return _instance;
}
}
 

Then should i synchronize it?

[r035198x]

Why not find an article about the Singleton and read it?

[JosAH]

@dmjpro
Think: a class is only loaded once by a classloader.

kind regards,

Jos

ps. btw it's 'Singleton', not 'SingleTone'.

[N002213F]

further to Jos' idea of synchronising the static method, the constructor should be private so that noone instantiates it except itself.

http://java.sun.com/developer/techni...ng/singletons/