Allow to create, only two objects for a class

Question

Hi,
This question is asked in my interview. In singleton concept only one object is created, likewise only two objects are created for a class.
For that i have write a code like this,
public class OnlyTwoObjects {
     private static OnlyTwoObjects a1;
     private static OnlyTwoObjects a2;
     public static int n = 0;
     public static OnlyTwoObjects getInstance() {
          if (a1 == null) {
               a1 = new OnlyTwoObjects();
               return a1;
          } else if (a2 == null) {
               a2 = new OnlyTwoObjects();
               return a2;
          } else if (n == 1) {
               return a1;
          } else if (n == 2) {
               return a2;
          return null;
} But they told this is not good way to do this.
I don't know how to do this, if any body knows kindly let me know.

Answer 1

vijay wrote:
But i will explain my code, in that code we are allowed to create only two objects, Maximum. Understood.
suppose both objects are created, then i will ask which object you need first or second, this is decided using the variable n if it is 1 then it will return the first object and it is 2 it will return the second object. sorry i didn't explain this in my previous post.This is your approach. Is this the requirement as well? Is it necessary that the user decide on which instance (first or second) is returned?Even if it was the requirement that the user decides which instance (first or second) is returned, with the original proposed implementation, the user only gets to decide which instance after calling getInstance() twice. If he calls getInstance() with n=2 when a1 is still null, he still gets a1. If he calls getInstance with n=1 when a2 is still null but a1 is non-null, then he gets a2. As is, he always gets a1 on the first call, a2 on the second call, and after that gets null unless he has set n to 1 or 2. (This explanation ignores any multi-threading issues that may come into play. This explanation is for a single thread.)