How do I restrict object creation not more than 3 in Java class?

Question

How do I restrict object creation not more than 3 in Java class?

Can you give me an idea of how I can to do it?

Answer 1

Instanciate your class via a factory (see design patterns) and limit it to 3 instances using a simple counter.

Answer 2

why not assign limInstance=null ; in else case in getLimInstance() ? in that case it will not provide obj3 duplicates ?

 public static synchronized InstanceClass getLimInstance()
{
        if(objCount < 3 ){
            limInstance = new InstanceClass();
        }
        else
        {
            limInstance=null;
        }
        return limInstance;
    }


public class LimitObjectCreationTest {


   public static void main(String[] args) {
    InstanceClass obj1 = InstanceClass.getLimInstance();
    InstanceClass obj2 = InstanceClass.getLimInstance();
    InstanceClass obj3 = InstanceClass.getLimInstance();
    InstanceClass obj4 = InstanceClass.getLimInstance();
    InstanceClass obj5 = InstanceClass.getLimInstance();
    InstanceClass obj6 = InstanceClass.getLimInstance();

    System.out.println(obj1);
    System.out.println(obj2);

    System.out.println(obj3);
    System.out.println(obj4);
    System.out.println(obj5);
    System.out.println(obj6);

    System.out.println(obj3);
  }

}

Result was this :

come.classinstance.InstanceClass@4a5ab2

come.classinstance.InstanceClass@1888759

come.classinstance.InstanceClass@6e1408

null

null

null

come.classinstance.InstanceClass@6e1408