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Singleton Design Pattern

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This example explores how to implement a SingletonPattern on a class in java.

Singleton Design Pattern

     

This example explores how to implement a SingletonPattern on a class in java.

The Singleton design pattern ensures that only one instance of a class is created, it provides a global point of access to the object and allow multiple instances in the future without affecting a singleton class's clients. To ensure that only one instance of a class is created we make SingletonPattern as static. getInstance() method returns a single instance of the class. We create a private default constructor to avoid outside modification.

This example gets instances of SingletonPattern two times but the method getInstance() will return the same object without creating a new one.

 The code of the program is given below:

public class SingletonPattern{
  private static SingletonPattern instance;
  private SingletonPattern(){} 
public static synchronized SingletonPattern getInstance(){
  if (instance == null)
  {
  instance = new SingletonPattern();
  }
  return instance;
  }
public static void main(String arg[]){
  System.out.println("The output of two instance:");
  SingletonPattern sp=new SingletonPattern();
  System.out.println("First Instance: "+sp.getInstance());
  sp=new SingletonPattern();
  System.out.println("Second Instance:"+sp.getInstance());
  }
}

The output of the program is given below:

C:\rajesh\kodejava>javac SingletonPattern.java
C:\rajesh\kodejava>java SingletonPattern
The output of two instance:
First Instance: SingletonPattern@3e25a5
Second Instance:SingletonPattern@3e25a5

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Posted on: July 6, 2007

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Comments
Ram
June 14, 2011
Singleton Comments

Good one for singleton pattern.
Shankar
October 5, 2011
Wrong

This is not a proper singleton patter arse
nitin
March 24, 2012
java

its usefully but i want full describtion.....
venu
June 4, 2012
Design pattern & Desing concepts

clearly explain above topics and realtime work environment where we use above topic
Kannan
July 9, 2012
its not singleton

its not singleton
bhagyashri hadkar
July 26, 2012
java

too good!!!
PD
August 24, 2012
FeedBack

Excellent Example! Thank You!
bondita
September 1, 2011
singleton design pattern

give some example of how to use the singleton class from another class...thanks
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