Java Reference
In-Depth Information
7
8
public class
Algorithms2
9
{
10
public static void
main(String[] args)
11
{
12
// initialize list1 and list2
13
String[] colors = {
"red"
,
"white"
,
"yellow"
,
"blue"}
;
14
List<String> list1 = Arrays.asList(colors);
15
ArrayList<String> list2 =
new
ArrayList<>();
16
17
list2.add(
"black"
);
// add "black" to the end of list2
18
list2.add(
"red"
);
// add "red" to the end of list2
19
list2.add(
"green"
);
// add "green" to the end of list2
20
21
System.out.print(
"Before addAll, list2 contains: "
);
22
23
// display elements in list2
24
for
(String s : list2)
25
System.out.printf(
"%s "
, s);
26
27
Collections.addAll(list2, colors);
// add colors Strings to list2
28
29
System.out.printf(
"%nAfter addAll, list2 contains: "
);
30
31
// display elements in list2
32
for
(String s : list2)
33
System.out.printf(
"%s "
, s);
34
35
// get frequency of "red"
int
frequency = Collections.frequency(list2,
"red"
);
System.out.printf(
"%nFrequency of red in list2: %d%n"
, frequency);
36
37
38
39
40
// check whether list1 and list2 have elements in common
boolean
disjoint = Collections.disjoint(list1, list2);
41
42
43
System.out.printf(
"list1 and list2 %s elements in common%n"
,
44
(disjoint ?
"do not have"
:
"have"
));
45
}
46
}
// end class Algorithms2
Before addAll, list2 contains: black red green
After addAll, list2 contains: black red green red white yellow blue
Frequency of red in list2: 2
list1 and list2 have elements in common
Fig. 16.13
|
Collections
methods
addAll
,
frequency
and
disjoint
. (Part 2 of 2.)
Line 14 initializes
list1
with elements in array
colors
, and lines 17-19 add
String
s
"black"
,
"red"
and
"green"
to
list2
. Line 27 invokes method
addAll
to add elements
in array
colors
to
list2
. Line 36 gets the frequency of
String
"red"
in
list2
using
method
frequency
. Line 41 invokes method
disjoint
to test whether
Collection
s
list1
and
list2
have elements in common, which they do in this example.
