asked on

iterating over elements of a HashMap

Hi,

I made a HashMap<String, Integer>. I want to iterator over all elements.

for (Iterator it = m_Table.values().iterator(); it.hasNext();) {
Map.Entry entry = (Map.Entry)it.next();
String strKey = (String)entry.getKey()
Integer nData = (Integer)entry.getValue() ;
}

This causes a runtime exception though... what's the right way to do it?

Thanks

ASKER CERTIFIED SOLUTION

ksivananth

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SOLUTION

Ajay-Singh

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DJ_AM_Juicebox

ASKER

Hmm they work. But I don't get the order in which the keys are extracted. In my HashMap, I have keys:

"xy"
"z"

That was the order in which they were entered into the map too. But when I iterate over them, they come out in:

"z"
"xy"

order?

Thanks

ksivananth

hashmap don't maintain the order, try using tree map!

ksivananth

sorry looks like, that will keep in a sorting order!

cmalakar

HashMap will not return the entries in order in which they were inserted..

If you want the same order in which you inserted, then you have to use.. LinkedHashMap

ksivananth

try use LinkedHashMap!

DJ_AM_Juicebox

ASKER

Ok I wrote my whole app (which is not that big really) using HashMap. The only operations I used from HashMap were get() and put().

So by switching the LinkedHashMap, I shouldn't have to change any of my use calls, right? The only difference is that now when I iterate over the elements, they'll come out in the order inserted?

Thanks

SOLUTION

cmalakar

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cmalakar

LinkedHashMap class is inherited from HashMap class