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Thread: Using class implicit toString() for array index

  1. #1
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    Default Using class implicit toString() for array index

    Hey all =)

    The title might not be what I really mean and for that I apologize..
    I'm asking this because its something that came up in a conversation I had with a colleague in my programming class

    Lets say I have this Class:

    public class Planet{
         int planetID;
     
         public Planet(int pID){
              planetID = pID;
         }
         public String toString(){
              return new Integer(planetID).toString();
         }
    }

    and this one:
    public class Testing{
         public static void main(String args[]){
              Planet mercury = new Planet(0);
              System.out.println(mercury);  //I know that this will return "0"
              Planet[] pArray = new Planet[9];
              pArray[mercury] = mercury;  //This is where my question lies
    }

    Saying in words, is it possible to use the implicit toString() every class has to directly return an int to make it usable in array indexing?

    I've already tried brainstorming with my colleague, and what we got was using something like(using above example):
    pArray[new Integer(mercury.toString())] = mercury;

    Is there an easier way to do this or is this simply stupid?


  2. #2
    Administrator copeg's Avatar
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    Default Re: Using class implicit toString() for array index

    This is somewhat a similar concept to a Hash, in which a particular property of an object (in java the returned value of hashCode()) is used to lookup that object from some sort of group of objects. In your case why mess with the string/integer converion intermediates - you could just write a get method for the planetID and use that get in the array
    pArray[mercury.getID()] = mercury;

  3. The Following User Says Thank You to copeg For This Useful Post:

    Quetzalma (February 3rd, 2010)

  4. #3
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    Default Re: Using class implicit toString() for array index

    I'll have a look about the Hash on the Java API..

    yeah, we thought of that too, we just wanted to know if there was a way to use directly (in this case) 'mercury' instead of calling methods to return what we needed to index the array, but I suppose that would be asking too much of java for a simple .getID() :p

    Thanks for the reply

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