Generic Collections - Java: How to Program Early Objects - page 706

Sorted ArrayList: [black, blue, pink, purple, red, tan, white, yellow]
Searching for: black
Found at index 0

Searching for: red
Found at index 4
Searching for: pink
Found at index 2
Searching for: aqua
Not Found (-1)
Searching for: gray
Not Found (-3)

Searching for: teal
Not Found (-7)

Fig. 16.12 | Collections method binarySearch . (Part 2 of 2.)

Lines 15-16 initialize list with an ArrayList containing a copy of the elements in
array colors . Collections method binarySearch expects its List argument's elements to
be sorted in ascending order, so line 18 uses Collections method sort to sort the list. If the
List argument's elements are not sorted, the result of using binarySearch is undefined . Line
19 outputs the sorted list. Lines 22-27 call method printSearchResults (lines 31-43) to
perform searches and output the results. Line 37 calls Collections method binarySearch
to search list for the specified key . Method binarySearch takes a List as the first argument
and an Object as the second argument. Lines 39-42 output the results of the search. An
overloaded version of binarySearch takes a Comparator object as its third argument, which
specifies how binarySearch should compare the search key to the List 's elements.

16.7.5 Methods addAll , frequency and disjoint
Class Collections also provides the methods addAll , frequency and disjoint . Collec-
tions method addAll takes two arguments—a Collection into which to insert the new
element(s) and an array that provides elements to be inserted. Collections method fre-
quency takes two arguments—a Collection to be searched and an Object to be searched
for in the collection. Method frequency returns the number of times that the second ar-
gument appears in the collection. Collections method disjoint takes two Collection s
and returns true if they have no elements in common . Figure 16.13 demonstrates the use
of methods addAll , frequency and disjoint .

1 // Fig. Fig. 16.13: Algorithms2.java

2 // Collections methods addAll, frequency and disjoint.

3 import java.util.ArrayList;

4 import java.util.List;

5 import java.util.Arrays;

6 import java.util.Collections;

Fig. 16.13 | Collections methods addAll , frequency and disjoint . (Part 1 of 2.)