HELP!! Can't read a map within a map

Question

Hey guys. I've been stuck on this issue for quite some time now and I haven't been able to figure this out. My structure that I am storing data in is in a map within a hashmap so its looks like the following
< k , <k,v>>
or in my case
<String, <Integer, Integer>>
and I want to iterator over each string pulling out all the map values or (<Integer, Integer>)
also each string has several <intger,integer> values in it.
<String, <Integer, Integer>>
<Ingeter,Integer>>
<Integer,Integer>>
So i thought about using a for each loop and using the Map.EntrySet
but I really don't know how to do this or understand it. Can someone clarify this up for me?
Thanks in advance.

Answer 1

what exactly does the iterator function do, if you don't mind me asking?You might find it useful to have a look at Sun's Tutorial on Collections. iterator() is dealt with near the start.
Your original post asked about how to use a for loop with the entry set. I realise I didn't address that. The following show similar ways of traversing a map:
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
public class IteratorEg {
    public static void main(String args[]) {
        Map<String,Integer> data = new HashMap<String,Integer>();
        data.put("first", 1);
        data.put("second", -1);
        data.put("last", 0);
        Iterator<String> it = data.keySet().iterator();
        while(it.hasNext()) {
            String key = it.next();
            int value = data.get(key);
            System.out.println(key + " --> " + value);
        for(String key :data.keySet()) {
            int value = data.get(key);
            System.out.println(key + " --> " + value);
        for(Map.Entry<String,Integer> entry :data.entrySet()) {
            System.out.println(entry.getKey() + " --> " + entry.getValue());
}As you can see either the key set or the entry set can be used. (It being a map there is an exact 1-1 correspondence between the keys and the entries.) And they can be traversed (gone through) using either the iterator that they provide, or using the new for loop syntax.