Collections and Generics - SCJP Sun Certified Programmer for Java Platform SE6 - page 475

25. System.out.println(“Index of milk is “ + index);
26. }
27. }
A breakdown of the ProductArraySearch program follows:
1. Line 4 declares a Comparator named DescriptionSorter that sorts Product objects in
lexicographical order of the description string.
2. Line 12 fills the products array with four Product objects.
3. Line 20 sorts the products array using the DescriptionSorter comparator. The for
loop on line 21 prints out the sorted array.
4. Line 24 searches the products array for the “milk” product, which appears at the end
of the array.
5. Line 25 prints out the value of index .
The output of the program is
bread 1.95
butter 2.75
eggs 4.0
milk 2.95
Index of milk is 3
Because “milk” is at the end of the array, its index is 3 . Notice that the products are
sorted in alphabetical order by description. Use the generic version of binarySearch when
you search an array sorted with a Comparator object.
Summary
This chapter covered the “Collections and Generics” objectives of the SCJP exam. The
goal of this chapter was to discuss the details of using the Java Collections Framework, a
collection of classes and interfaces in the java.util package that implement common data
structures like lists, maps, and sets. The collection's classes and interfaces use generics,
which provide a compile-time type safety for simplifying the use of collections.
The Collection interface is the parent interface of List , Set , and Queue . The map
data structures implement the Map interface. A list is an ordered collection of elements
that allows duplicate entries. The List implementations include ArrayList , LinkedList ,
Vector , and Stack . A set is a collection that does not allow duplicate entries. The Set
implementations are HashSet , LinkedHashSet , and TreeSet . A queue is a collection
that orders its elements in a specifi c order for processing. The Queue implementations
include LinkedList , PriorityQueue , and ArrayDeque . A map is a collection that maps
keys to values, with no duplicate keys allowed. The Map implementations are HashMap ,
LinkedHashMap , and TreeMap .