Do you mean with dictionary something to map keys to values? Java uses Maps for this:
import java.util.*;
...
Map<Foo, Bar> myMap = new HashMap<Foo, Bar>();
Foo key = ...;
Bar value = ...;
myMap.put(key, value);
value = myMap.get(key);
Tutorial:
http://java.sun.com/docs/books/tutorial/collections/index.html
http://java.sun.com/docs/books/tutorial/collections/interfaces/map.html
-Puce