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  1. //// Thread-safe Singleton with Double-Checked Locking
  2. class singleton{
  3.     private static volatile singleton instance;
  4.     private singleton(){
  5.         System.out.println("singleton instance is created");
  6.     }
  7.     public static singleton getInstance(){
  8.         if(instance==null)
  9.         {
  10.             synchronized(singleton.class){
  11.                 if(instance==null)
  12.                 {
  13.                     instance = new singleton();
  14.                 }
  15.             }
  16.         }
  17.         return instance;
  18.     }
  19.     void method()
  20.     {
  21.         System.out.println("Hello from Singleton!");
  22.     }
  23. }
  24.  
  25. public class Main{
  26.     public static void main(String[] args)
  27.     {
  28.         singleton obj1 = singleton.getInstance();
  29.         singleton obj2 = singleton.getInstance();
  30.  
  31.         obj1.method();
  32.  
  33.         if(obj1==obj2)
  34.         {
  35.             System.out.println("Both references point to the same instance!");
  36.         }
  37.     }
  38. }
Success #stdin #stdout 0.07s 54524KB
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Standard input is empty
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singleton instance is created
Hello from Singleton!
Both references point to the same instance!
https://ideone.com/mLoRuM
language:
Java (HotSpot 12)
created:
2 days ago
visibility:
public

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