Question

I have code I am working on, but I am having issues populating the HashMap of HashMaps. The declaration goes as thus;

HashMap<Games, HashMap<Store, Integer>> myMap = new HashMap<Games, HashMap<Store,   Integer>>();

Where Game and Store are separate object classes, with only a class variable title.

How do I create instances of the objects in the HashMaps and also populate the two hashmaps. Because I need to tag an Integer to the game in a particular store. Whereas there are different stores and different games in each store.

Thanks in Advance

Edit

Games Class

package gameStore;

public class Games {
    private String title;

    public Games(String inTitle){
        setTitle(inTitle);
    }
    private String getTitle() {
        return title;
    }
    private void setTitle(String title) {
        this.title = title;
    }
}

Stores Class

package gameStore;

public class LocalStores {
    private String nameOfStore;

    public LocalStores(String inNameOfStore){
        setNameOfStore(inNameOfStore);
    }
    private void setNameOfStore(String nameOfStore){
        this.nameOfStore = nameOfStore;
    }
}

Answer 1

I would do something like this:

void addToMap(Games games, Store store, int value) {
    HashMap<Store,Integer> m = myMap.get(games);
    if (m == null) {
        m = new HashMap<Store,Integer>();
        myMap.put(games, m);
    }
    m.put(store, value);
}

UPDATE:

Since Games and Store are both used as keys to a HashMap, I would recommand that you add the hashCode and equals methods:

Games:

public int hashCode() {
    return title.hashCode();
}

public boolean equals(Object obj) {
    if (!(obj instanceof Games)) {
        return false;
    }
    Games other = (Games)obj;
    return title.equals(other.title);
}

LocalStores:

public int hashCode() {
    return nameOfStore.hashCode();
}

public boolean equals(Object obj) {
    if (!(obj instanceof LocalStores)) {
        return false;
    }
    LocalStores other = (LocalStores)obj;
    return nameOfStore.equals(other.nameOfStore);
}

Now, to keep it simple, let’s say that each line of your input file contains three fields separated by tabs: the games’ title, the store’s name, and the integer value. You would read it as follows:

InputStream stream = new FileInputStream("myfile");
try {
    Reader reader = new InputStreamReader(stream, "UTF-8"); // or another encoding
    try {
        BufferedInputStream in = new BufferedInputStream(reader);
        try {
            String line = in.readLine();
            while (line != null) {
                String[] fields = line.split("[\\t]");
                if (fields.length == 3) {
                    addToMap(new Games(fields[0]), new LocalStores(fields[1]), Integer.parseInt(fields[2]));
                }
                line = in.readLine();
            }
        } finally {
            in.close();
        }
    } finally {
        reader.close();
    }
} finally {
    stream.close();
}