Limited no of Objects

[faisal hameed]

Hi Ranchers ! Can we restrict someone to create a limited objects of a class ?

[Miklos Szeles]

Yes you can. You can create a private constructor for your class and you can create a static factory method which creates an instance of your object. In this method you can increment a counter, and throw an exception/return null, when the limit is exceeded.

[Rahul P Kumar]

use singleton pattern, there you maintain a global counter, which tracks the number of objects created and keeps a reference of them. Oncecounter exceeds, you do not allow to create any further object of your class.

[leroy tsruya]

sorry my mistake...

[sujith Acharya]

yes you can. Give the responsibility of creating the object of the class, to the class itself (which takes care how many objects have been created) by making its constructor private and creating one public static method which creates the object of the class and returns to the client.

   
class A{
    private static int count;
    private static int MAX_COUNT = 5;
    private A(){
    }
     
    public static A getObject(){
        if(count < MAX_COUNT){
              count ++;
              return new A()
        }
        else{ 
          // do what you like
        }
    }
}

[Campbell Ritchie]

Agree. That is a variant of the singleton pattern.

[Gerbrand van Dieijen]

sujith Acharya wrote:

   
class A{
..

Minor note: the above code is not thread save. So in case you're accessing getObject from multiple threads (which usually happens when used within a webapplication) you'll need to add the synchronized keyword:

   
class A{
...
    public synchronized static A getObject(){
...
}

Else you'll might get more objects than wanted, if getObject gets executed at exactly the same time.