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  1. /**
  2.  * Testing singleton creation and clean instance 
  3.  * 
  4.  */
  5. import java.util.*;
  6. import java.lang.*;
  7. import java.io.*;
  8.  
  9. /* Name of the class has to be "Main" only if the class is public. */
  10. class Ideone
  11. {
  12. 	public static void main (String[] args) throws java.lang.Exception
  13. 	{
  14. 		ASingletonClass a = ASingletonClass.getInstance();
  15. 		System.out.println("Instance reference of a: "+a);
  16. 		ASingletonClass b = ASingletonClass.getInstance();
  17. 		System.out.println("Instance reference of b: "+b+" which is equal to a");
  18. 		b.clear();
  19. 		System.out.println("Instances are still same");
  20. 		System.out.println("Instance reference of a: "+a);
  21. 		System.out.println("Instance reference of b: "+b+" which is equal to a");
  22.  
  23. 		System.out.println("After getting instances again, the references changed:");
  24. 		a = ASingletonClass.getInstance();
  25. 		System.out.println("Instance reference of a: "+a);
  26. 		b = ASingletonClass.getInstance();
  27. 		System.out.println("Instance reference of b: "+b+" which is equal to a");
  28.  
  29. 	}
  30. }
  31.  
  32. class ASingletonClass
  33. { 
  34.     private static ASingletonClass instance = null; 
  35.  
  36.     private ASingletonClass() {} 
  37.  
  38.     public static ASingletonClass getInstance() 
  39.     { 
  40.         if (instance == null) 
  41.             instance = new ASingletonClass(); 
  42.         return instance; 
  43.     } 
  44.     public static void clear()
  45. 	{
  46. 		instance = null;
  47. 	}
  48. }
Success #stdin #stdout 0.11s 36192KB
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Standard input is empty
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Instance reference of a: ASingletonClass@816f27d
Instance reference of b: ASingletonClass@816f27d which is equal to a
Instances are still same
Instance reference of a: ASingletonClass@816f27d
Instance reference of b: ASingletonClass@816f27d which is equal to a
After getting instances again, the references changed:
Instance reference of a: ASingletonClass@7229724f
Instance reference of b: ASingletonClass@7229724f which is equal to a
https://ideone.com/me1NvQ
language:
Java (HotSpot 12)
created:
4 years ago
visibility:
public

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