Advanced Data Structures - Java Concepts - page 962

706

Figure 4

Map Classes and Interfaces in the Standard Library

Use the put method to add an association:

favoriteColors.put("Juliet", Color.PINK);

You can change the value of an existing association, simply by calling put again:

favoriteColors.put("Juliet", Color.RED);

The get method returns the value associated with a key.

Color julietsFavoriteColor =
favoriteColors.get("Juliet");

If you ask for a key that isn't associated with any values, then the get method returns
null .

To remove a key and its associated value, use the remove method:

favoriteColors.remove("Juliet");

Sometimes you want to enumerate all keys in a map. The keySet method yields the
set of keys. You can then ask the key set for an iterator and get all keys. From each
key, you can find the associated value with the get method. Thus, the following
instructions print all key/value pairs in a map m :

Set<String> keySet = m.keySet();
for (String key : keySet)