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how to make single instance of a class?

Kartik Mahadevan
Ranch Hand

Joined: Feb 16, 2005
Posts: 47
I have to make a class which can be created only once .How do I do it ?

BalajiS Sridharan

Joined: Aug 29, 2005
Posts: 2
make the constructor private and have a public static method which will instantiate a instance but before instantiating check whether the variable is null or not


public class SingleInstance
private SingleInstance()


private singleInstance;

public static SingleInstance returnSingleInstance()
if(singleInstance == null)
singleInstance = new SingleInstance();
return singleInstance;

[ September 05, 2005: Message edited by: BalajiS Sridharan ]
David Ulicny
Ranch Hand

Joined: Aug 04, 2004
Posts: 724
Just implement Singleton design pattern.

SCJP<br />SCWCD <br />ICSD(286)<br />MCP 70-216
It is sorta covered in the JavaRanch Style Guide.
subject: how to make single instance of a class?
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