Hello,

I have a questions about how the contains() method works for a class in Collection framework with a user defined object. Do I have to do something special?

I tried the following example. But the output is not what I expected.

--------------- CODE --------------------
import java.util.*;

class Lane
{    int SNode, DNode;       
    public Lane(int SN, int DN)
    {    SNode=SN; DNode=DN;    }

    public boolean equals(Lane o)
    {    if(o.SNode==SNode && o.DNode==DNode) return true;
        else return false;
    }
};

class Bundle
{    HashSet<Lane> Lanes;
   
    public Bundle(){    Lanes=new HashSet<Lane>();    }

    public boolean add(Lane l){    return Lanes.add(l);    }

    public boolean contains(Lane l){    return Lanes.contains(l);    }

    public void printAll()
    {    System.out.print("[ ");
        for(Lane l : Lanes){    System.out.print("("+l.SNode+","+l.DNode+") ");    }
        System.out.println("]");
    }
};

public class Test
{   
    public static void main(String[] args)
    {    Lane L1=new Lane(1,2), L2=new Lane(1,3);
        Bundle B=new Bundle();
        B.add(L1);
        B.add(L2);
        B.printAll();
        if(B.contains(L2)) System.out.println("Bundle has L2");
        if(B.contains(new Lane(1,3))) System.out.println("Bundle has (1,3)");
    }
}

-------------- OUTPUT ------------
[ (1,3) (1,2) ]
Bundle has L2
---------------------------------

I was expecting to see "Bundle has (1,3)" in the output. My impression was that contains method internally calls equals method of the object concerned, so I even defined my own equals(). Still it did not work. What am I missing?

Also, one secondary question. I am sure this question has been discussed in many texts and newsgroup messages, but with google I couldn't find. What will be the exact set of keywords for my case to search? I tried [java "contains method" "user defined object"], [java Collection "contains method"] etc.

Thanks.