import java.util.*;
// Declare the variable using the interface of the object for flexibility.
// Non-primative data types only.
Map<Integer, String> mambo = new TreeMap<Integer, String>();
mambo.put(key, value);
// TreeMap will be sorted by key.
// Work with any comparable object as a key.
mambo.put(1, "Monica");
mambo.put(2, "Erica");
mambo.put(3, "Rita");