Java Reference
In-Depth Information
Viewing Arrays as
List
s and Converting
List
s to Arrays
Figure 16.4 uses
Arrays
method
asList
to view an array as a
List
and uses
List
method
toArray
to get an array from a
LinkedList
collection. The program calls method
asList
to create a
List
view of an array, which is used to initialize a
LinkedList
object, then adds
a series of
String
s to the
LinkedList
and calls method
toArray
to obtain an array con-
taining references to the
String
s.
1
// Fig. 16.4: UsingToArray.java
2
// Viewing arrays as Lists and converting Lists to arrays.
3
import
java.util.LinkedList;
4
import
java.util.Arrays;
5
6
public class
UsingToArray
7
{
8
// creates a LinkedList, adds elements and converts to array
9
public static void
main(String[] args)
10
{
11
String[] colors = {
"black"
,
"blue"
,
"yellow"
};
12
LinkedList<String> links =
new
LinkedList<>(Arrays.asList(colors));
13
14
links.addLast(
"red"
);
// add as last item
links.add(
"pink"
);
// add to the end
links.add(
3
,
"green"
);
// add at 3rd index
links.addFirst(
"cyan"
);
// add as first item
15
16
17
18
19
// get LinkedList elements as an array
colors = links.toArray(
new
String[links.size()]);
20
21
22
System.out.println(
"colors: "
);
23
24
for
(String color : colors)
25
System.out.println(color);
26
}
27
}
// end class UsingToArray
colors:
cyan
black
blue
yellow
green
red
pink
Fig. 16.4
|
Viewing arrays as
List
s and converting
List
s to arrays.
Line 12 constructs a
LinkedList
of
String
s containing the elements of array
colors
.
Arrays
method
asList
returns a
List
view of the array, then uses that to initialize the
LinkedList
with its constructor that receives a
Collection
as an argument (a
List
is a
Collection
). Line 14 calls
LinkedList
method
addLast
to add
"red"
to the end of
links
.
Lines 15-16 call
LinkedList
method
add
to add
"pink"
as the last element and
"green"
as the element at index
3
(i.e., the fourth element). Method
addLast
(line 14) functions
