Singleton Implementation Java Code

Singleton.java

public class Singleton
{
// Static member holds only one instance of the Singleton class
private static Singleton singletonInstance;

// SingletonExample prevents any other class from instantiating
private Singleton()
{

}

// Providing Global point of access
public static Singleton getSingletonInstance()
{
if( null == singletonInstance )
{
singletonInstance = new Singleton();
System.out.println("Inside null check , Object is Created : "                
                                                                                +singletonInstance.toString());
         System.out.println(" -------------------------------------------------- ");
}
return singletonInstance;
}

public void printSingleton()
{
System.out.println("Inside print Singleton object : " +singletonInstance.toString());
System.out.println("");
}

}

SingletonPatternDemo.java

public class SingletonPatternDemo

{

public static void main( String[] args )

{

Singleton.getSingletonInstance().printSingleton();

Singleton.getSingletonInstance().printSingleton();

Singleton.getSingletonInstance().printSingleton();

}

}

Output

Inside null check , Object is Created : Singleton@addbf1

 -----------------------------------------------------

Inside print Singleton object : Singleton@addbf1

Inside print Singleton object : Singleton@addbf1

Inside print Singleton object : Singleton@addbf1

See also:

Singleton Design Pattern - Introduction

Singleton Design Pattern - Implementation

Singleton Design Pattern - key Points

All Design Patterns Links