How to get value from TreeMap in Java?

Question

My problem is can't get an object "Item" (value) from my Treemap. I need send that info to my GUI class and display it in JList to get a select list, so can easily select and add songs to playlist, but only what I get as an output is "01, 02, 03, 04, 05" (key). Please help, because I'm beginner and have no idea what to do.

public class LibraryData {

private static class Item {


    Item(String n, String a, int r) {
        name = n;
        artist = a;
        rating = r;
    }

    // instance variables 
    private String name;
    private String artist;
    private int rating;
    private int playCount;

    public String toString() {
        return name + " - " + artist;
    }
}


private static Map<String, Item> library = new TreeMap<String, Item>();


static {
    library.put("01", new Item("How much is that doggy in the window", "Zee-J", 3));
    library.put("02", new Item("Exotic", "Maradonna", 5));
    library.put("03", new Item("I'm dreaming of a white Christmas", "Ludwig van Beethoven", 2));
    library.put("04", new Item("Pastoral Symphony", "Cayley Minnow", 1));
    library.put("05", new Item("Anarchy in the UK", "The Kings Singers", 0));
}


public static String[] getLibrary() {
String [] tempa = (String[]) library.keySet().toArray(new String[library.size()]);
return tempa;
}

SOLUTION:

Because I've to pass the values to another class:

JList tracks = new JList(LibraryData.getLibrary());

I made something like that and it's works

public static Object[] getLibrary() {
Collection c = library.values();
return c.toArray(new Item[0]);

Thank You guys, after 10 hours I finally done it! }

Answer 1

With this code that you have:

String [] tempa = (String[]) library.keySet().toArray(new String[library.size()]);

You are getting all keys from the map. If you want all values, then use:

library.values();

Finally, if you need to get a value by key use V get(Object key):

library.get("01");

Which will return you the first Item from the map.

It's not very clear which one of these you want, but basically these are the options.

** EDIT **

Since you want all values you can do this:

library.values().toArray()

JList expects an array or vector of Object so this should work.