Topic: ArrayList Restriction

ArrayList Restriction

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Posted By: Shikhar_Rastogi
Posted On: Sunday, September 4, 2005 08:28 AM

Can i restrict ArrayList someway for adding only Integer elements?

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Re: ArrayList Restriction

Posted By: srini_vasan
Posted On: Monday, September 19, 2005 09:31 AM

Upto java1.4 , it is not possible to restrict
the ArrayList to add only integers.

But we can make ArrayList to add Integers only ,

by using some wrapper class as follows

  import java.util.ArrayList;

public class IntegerArrayList extends ArrayList
{
     
   public boolean add(Object o)
   {
        if(o instanceof Integer)
        {
            return super.add(o);
        }
        else
        {
            return false;
        }  

    }
 
  // similarly u should override  other methods of ArrayList

}

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Re: ArrayList Restriction

Posted By: Jagadeesh_Kumar
Posted On: Monday, September 5, 2005 03:00 AM

Hi Shikar,
You cant restrict array list to add a specific primitive type like int, float etc. But u can just manually check the object type using IF condition before adding the type to arraylist.

Regards,
Jagadeesh

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Re: ArrayList Restriction

Posted By: WarnerJan_Veldhuis
Posted On: Sunday, September 4, 2005 01:04 PM

If you use Java5, yes: List myList = new ArrayList(); It's called "Generics"

If you use Java1.4 or less, no, unless you create a subclass of ArrayList, and override the add()-related methods like this:


public void add(Integer a) {
   super.add(a);
}

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