Java™ How To Program (Early Objects), Tenth Edition

Section 16.11 Maps

• Maps (p. 714) store key–value pairs and cannot contain duplicate keys. HashMaps (p. 714) and Hashtables (p. 714) store elements in a hash table, and TreeMaps (p. 714) store elements in a tree.

• HashMap takes two type arguments—the type of key and the type of value.

• HashMap method put (p. 717) adds a key–value pair to a HashMap. Method get (p. 717) locates the value associated with the specified key. Method isEmpty (p. 718) determines if the map is empty.

• HashMap method keySet (p. 718) returns a set of the keys. Map method size (p. 718) returns the number of key–value pairs in the Map.

• Interface SortedMap (p. 714) extends Map and represents a map that maintains its keys in sorted order. Class TreeMap implements SortedMap ...