Generic Collections - Java: How to Program Early Objects - page 694

removeItems (lines 64-68) to remove the range of elements starting at index 4 up to, but
not including, index 7 of the list. Line 37 calls method printReversedList (lines 71-80)
to print the list in reverse order.
Method convertToUppercaseStrings
Method convertToUppercaseStrings (lines 52-61) changes lowercase String elements
in its List argument to uppercase String s. Line 54 calls List method listIterator to
get the List 's bidirectional iterator (i.e., one that can traverse a List backward or for-
ward ). ListIterator is also a generic class. In this example, the ListIterator references
String objects, because method listIterator is called on a List of String s. Line 56 calls
method hasNext to determine whether the List contains another element . Line 58 gets the
next String in the List . Line 59 calls String method toUpperCase to get an uppercase
version of the String and calls ListIterator method set to replace the current String
to which iterator refers with the String returned by method toUpperCase . Like method
toUpperCase , String method toLowerCase returns a lowercase version of the String .
Method removeItems
Method removeItems (lines 64-68) removes a range of items from the list. Line 67 calls
List method subList to obtain a portion of the List (called a sublist ). This is called a
range-view method , which enables the program to view a portion of the list. The sublist
is simply a view into the List on which subList is called. Method subList takes as argu-
ments the beginning and ending index for the sublist. The ending index is not part of the
range of the sublist. In this example, line 35 passes 4 for the beginning index and 7 for the
ending index to subList . The sublist returned is the set of elements with indices 4 through
6 . Next, the program calls List method clear on the sublist to remove the elements of
the sublist from the List . Any changes made to a sublist are also made to the original List .
Method printReversedList
Method printReversedList (lines 71-80) prints the list backward. Line 73 calls List
method listIterator with the starting position as an argument (in our case, the last ele-
ment in the list) to get a bidirectional iterator for the list. List method size returns the
number of items in the List . The while condition (line 78) calls ListIterator 's hasPre-
vious method to determine whether there are more elements while traversing the list back-
ward . Line 79 calls ListIterator 's previous method to get the previous element from
the list and outputs it to the standard output stream.
Views into Collections and Arrays Method asList
Class Arrays provides static method asList to view an array (sometimes called the back-
ing array ) as a List collection. A List view allows you to manipulate the array as if it were
a list. This is useful for adding the elements in an array to a collection and for sorting array
elements. The next example demonstrates how to create a LinkedList with a List view
of an array, because we cannot pass the array to a LinkedList constructor. Sorting array
elements with a List view is demonstrated in Fig. 16.7. Any modifications made through
the List view change the array, and any modifications made to the array change the List
view. The only operation permitted on the view returned by asList is set , which changes
the value of the view and the backing array. Any other attempts to change the view (such
as adding or removing elements) result in an UnsupportedOperationException .