Question

I have the following code which adds some arrays to a hashmap but then I want access those arrays to do some work on them later. I’ve gotten this far but can’t figure the rest out to make it work….

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map.Entry;

    public static void main(String[] args) {

        String[][] layer1 = {
            {"to1", "TYPE1", "start"}, 
            {"to2", "TYPE1", "start"}
        };

        String[][] layer2 = {
            {"to3", "TYPE2" ,"item1"},
            {"to3", "TYPE2" ,"item2"}
        };

        HashMap<String,Object> hashMap = new HashMap<String,Object>();
        hashMap.put("layer1", layer1);
        hashMap.put("layer2", layer2);

        Iterator<Entry<String, Object>> iterator = hashMap.entrySet().iterator();
        while(iterator.hasNext()){
            hashMap.values().toArray();
            for (???) {
                // lets print array here for example
            }
        }        

    }

Answer 1

Smells like homework, but a few suggestions –

• there’s no reason for your Hashmap to be of the form <String,Object> – make it <String, String[][]> , as that’s what you’re storing.

You’re iterating twice. You either
– iterate through the map, either the keys, values or entries. Each item is an iterator return value, e.g.

for (String[][] s:map.values()){
 ...
}

• hashmap.values.toArray gives you all of the contents, which is the same thing your iterator is doing.

• if you’re only iterating through the contents, then you’re not really using a map, as you’re never making use of the fact that your values are available by key.