Collections and Generics - SCJP Sun Certified Programmer for Java Platform SE6 - page 468

13. System.out.print(i + “ “);
14. }
15. System.out.println();
16. int index = Collections.binarySearch(list, new Integer(5));
17. if(index >= 0) {
18. System.out.println(“5 found at index “ + index);
19. } else {
20. System.out.println(“5 not found”);
21. }
The Integer class implements Comparable , and the method call on line 16 invokes the
Comparable version of the binarySearch method. The value of index is the location in
list where one of the 5 s appears, or a negative value if list does not contain a 5 . Here is a
sample output of the previous statements:
0 0 0 1 1 2 3 3 3 5 5 5 5 5 6 8 8 9 9 9
5 found at index 9
If more than one element is found, the index returned is for one of the elements, but
there is no guarantee as to which one.
The following example demonstrates the other version of binarySearch that uses a
Comparator object. Use the Comparator version of binarySearch when the elements in the
list do not implement the Comparable interface. For example, suppose we have a list of
Product objects based on the Product class from earlier in this chapter:
public class Product {
String description;
double price;
int id;
public Product(String d, double p, int i) {
description = d;
price = p;
id = i;
}
//remainder of class definition...
}
A Comparator object is required to sort and search a list of Product objects, as
demonstrated by the following program. Study the code and see if you can determine its
result:
1. import java.util.*;
2.
3. public class ProductSearch {