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Java Example program to restrict a class from creating not more than three objects

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instanceof java

Posts: 576
Nickname: instanceof
Registered: Jan, 2015

instanceof java is a java related one.
Java Example program to restrict a class from creating not more than three objects Posted: Mar 14, 2016 2:22 PM
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This post originated from an RSS feed registered with Java Buzz by instanceof java.
Original Post: Java Example program to restrict a class from creating not more than three objects
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Question: How to restrict a class from creating multiple objects?

  • Restring a class from creating multiple objects or restricting class from creating not more than three objects this type of interview questions will come for experience interview or written tests.

  • Yes we can restrict a class from creating multiple objects.
  • As we know using singleton we can restrict a class from creating multiple objects it will create single object and share it.
  • Same design pattern we can apply here with counter 
  • In this we will take a static variable counter to check how many objects created
  • As we can access static variables in constructor and static variables are class level we can stake help of static variable to count number object created.
  • First three time we will create new objects and forth time we need to return 3rd object reference. if we don't want same object 4th time we can return null
  • By printing the hashcode() of the object we can check how many objects created. 
  •  

Basic java example program to restrict a class from not to create more than three instances




  1. package com.instanceofjava;
  2.  
  3. public class RestrictObjectCreation{

  5. private static RestrictObjectCreationobject;
  6. public static int objCount = 0;
  7.  
  8. private RestrictObjectCreation()
  9. {
  10.      System.out.println("Singleton(): Private constructor invoked");
  11.  
  12. objCount  ++;
  14. }
  15.  
  16. public static RestrictObjectCreation getInstance()
  17. {
  18.  
  19. if (objCount < 3)
  20. {
  21.  
  22. object = new RestrictObjectCreation();
  23.  
  24.  }
  25.  
  26. return object;
  27.  
  28. }
  29.  
  30. }
     

  1. package instanceofjava;
  2.  
  3. public class Test{

  5. public static void main(String args[]) {
  6.  
  7. RestrictObjectCreation obj1= RestrictObjectCreation.getInstance();
  8. RestrictObjectCreation obj2= RestrictObjectCreation.getInstance();
  9. RestrictObjectCreation obj3= RestrictObjectCreation.getInstance();
  10. RestrictObjectCreation obj4= RestrictObjectCreation.getInstance();
  11. RestrictObjectCreation obj5= RestrictObjectCreation.getInstance();
  12.  
  13. System.out.println(obj1.hashCode());
  14. System.out.println(obj2.hashCode());
  15. System.out.println(obj3.hashCode());
  16. System.out.println(obj4.hashCode());
  17. System.out.println(obj5.hashCode());
  18.  
  19. }
  20. }

Output:

  1. RestrictObjectCreation(): Private constructor invoked
  2. RestrictObjectCreation(): Private constructor invoked
  3. RestrictObjectCreation(): Private constructor invoked
  4. 705927765
  5. 366712642
  6. 1829164700
  7. 1829164700
  8. 1829164700


restrict from creating multiple objects

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