Java Reference
In-Depth Information
a different order. Line 18 calls
Collections
's method
sort
to order the
List
in descend-
ing order. The
static
Collections
method
reverseOrder
returns a
Comparator
object
that orders the collection's elements in reverse order.
1
// Fig. 16.7: Sort2.java
2
// Using a Comparator object with method sort.
3
import
java.util.List;
4
import
java.util.Arrays;
5
import
java.util.Collections;
6
7
public class
Sort2
8
{
9
public static void
main(String[] args)
10
{
11
String[] suits = {
"Hearts"
,
"Diamonds"
,
"Clubs"
,
"Spades"
};
12
13
// Create and display a list containing the suits array elements
14
List<String> list = Arrays.asList(suits);
// create List
15
System.out.printf(
"Unsorted array elements: %s%n"
, list);
16
17
// sort in descending order using a comparator
Collections.sort(list, Collections.reverseOrder());
18
19
System.out.printf(
"Sorted list elements: %s%n"
, list);
20
}
21
}
// end class Sort2
Unsorted array elements: [Hearts, Diamonds, Clubs, Spades]
Sorted list elements: [Spades, Hearts, Diamonds, Clubs]
Fig. 16.7
|
Collections
method
sort
with a
Comparator
object.
Sorting with a
Comparator
Figure 16.8 creates a custom
Comparator
class, named
TimeComparator
, that implements
interface
Comparator
to compare two
Time2
objects. Class
Time2
, declared in Fig. 8.5, rep-
resents times with hours, minutes and seconds.
1
// Fig. 16.8: TimeComparator.java
2
// Custom Comparator class that compares two Time2 objects.
3
import
java.util.Comparator;
4
5
public class
TimeComparator
implements
Comparator<Time2>
6
{
7
@Override
8
public
int
compare(
Time2 time1 Time2 time2
,
)
9
{
10
int
hourDifference = time1.getHour() - time2.getHour();
11
12
if
(hourDifference !=
0
)
// test the hour first
13
return
hourCompare;
Fig. 16.8
|
Custom
Comparator
class that compares two
Time2
objects. (Part 1 of 2.)
