problem with retriving values from hashtable

[Murali Jaya Rao]

hi all,

i am storing string array as keys and arraylist as values in my hashtable.when i retrieving the values at particular keys am getting values of last key index to all of my key values.that means the last key values(arraylist)are reflected to all while displaying.can anyone help regarding this

Thanks & regards,
Murali

[patanjali yogi]

Your keys are String arrays. Java computes the hashcode of the key. So if the string is for e.g "abc" the hashcode could be "abc".hascode(). Not sure how will the Java compute hash code of a string array. You may have to overwrite the hashCode() method.

[Nitesh Kant]

Kindly post the code to help us help you better.
{Use code tags while posting code}
I have a strong feeling that you are assigning the values to the Map in a loop and you are not initializing the arraylist for every iteration.

patanjali: You may have to overwrite the hashCode() method.

You mean override? True that an array is a first class object in java but the implementation is not open for modifications. So, one can not override hashcode() method for arrays.
[ February 25, 2008: Message edited by: Nitesh Kant ]

[Murali Jaya Rao]

if (tmpsub.getSubheaderName().equalsIgnoreCase(nodes[i])){

Vector tmpvecvpd = tmpsub.getVPDElements();
Enumeration vpd = tmpvecvpd.elements();
while(vpd.hasMoreElements()){
VPDElement tmpvpd = (VPDElement)vpd.nextElement();
list.add(tmpvpd.getName());
list.add(tmpvpd.getDefaultSize());
list.add(tmpvpd.getType());
list.add(tmpvpd.getActualSize());
list.add(tmpvpd.getActualValue());
list.add(tmpvpd.getDescription());
}
hash.put(nodes[i], list);
i++;

list.clear();
}
}

}
Enumeration e = hash.keys();
Object obj;
while (e.hasMoreElements()) {
obj=e.nextElement();
System.out.println("hashtable " + obj + ": " + hash.get(obj));

}
}

this is the code,node[i] of type string array and list is of type arraylist.go through the code if any doubts post me.

[Jim Yingst]

It looks like "list" always refers to the same single list, which you keep clearing and then putting new items in. All the values in the map are references to the same single list. Instead, you want each value to be a different list. Create a new ArrayList() (or whatever kind of List you're using) for each set of values you want to put in the map.

Also, please follow the link Nitesh gave which explains how to use code tags. They're very useful for making your code readable in this forum.
[ February 25, 2008: Message edited by: Jim Yingst ]

[Murali Jaya Rao]

Thanks Jim Yingst ,now i am getting the result what i want.from next time onwards i will definitely follow code tags.
Thanks & Reggards,
Murali.

[Jim Yingst]

By the way, it is incorrect to say that your keys here are String arrays. The variable nodes refers to a String array, but nodes[ i ] refers to a single element in the array, which is just a single String, not an array. That's good, because arrays really cannot be used successfully as keys in a Map (Hashtable in this case). The fact is that equals() and hashCode() for an array object are not suitable for use as a key, and you can't override those methods in an array. You'd have been better off with a custom class that contained an array. However, it turns out that this discussion was unnecessary, because your keys are not arrays at all.
[ February 25, 2008: Message edited by: Jim Yingst ]