Java Reference
In-Depth Information
Processing the Stream Pipeline
When
forEach
is called (line 58), the stream pipeline is processed. First, line 55 produces
an intermediate
IntStream
containing only the odd values. Next, line 56 multiplies each
odd integer by
10
. Then, line 57 sorts the values and line 58 displays each element.
rangeClosed
If you need an
ordered sequence
of
int
values, you can create an
IntStream
containing such
values with
IntStream
methods
range
(line 63 of Fig. 17.5) and
rangeClosed
(line 67).
Both methods take two
int
arguments representing the range of values. Method
range
produces a sequence of values from its first argument up to, but
not
including its second
argument. Method
rangeClosed
produces a sequence of values including
both
of its argu-
ments. Lines 63 and 67 demonstrate these methods for producing sequences of
int
values
from 1-9 and 1-10, respectively. For the complete list of
IntStream
methods, visit:
[This section demonstrates how lambdas and streams can be used to simplify programming
tasks that you learned in Chapter 7, Arrays and ArrayLists.]
Just as class
IntStream
's method
of
can create an
IntStream
from an array of
int
s, class
Array
's
stream
method can be used to create a
Stream
from an array of objects.
Figure 17.6 performs
filtering
and
sorting
on a
Stream<Integer>
, using the same tech-
niques you learned in Section 17.3. The program also shows how to
collect
the results of a
stream pipeline's operations into a new collection that you can process in subsequent state-
ments. Throughout this example, we use the
Integer
array
values
(line 12) that's initial-
ized with
int
values—the compiler
boxes
each
int
into an
Integer
object. Line 15 displays
the contents of
values
before we perform any stream processing.
1
// Fig. 17.6: ArraysAndStreams.java
2
// Demonstrating lambdas and streams with an array of Integers.
3
import
java.util.Arrays;
4
mport
java.util.Comparator;
i
5
import
java.util.List;
6
7
8
import
java.util.stream.Collectors;
public class
ArraysAndStreams
9
{
10
public static void
main(String[] args)
11
{
12
Integer[] values = {
2
,
9
,
5
,
0
,
3
,
7
,
1
,
4
,
8
,
6
};
13
14
// display original values
15
System.out.printf(
"Original values: %s%n"
, Arrays.asList(values));
Fig. 17.6
|
Demonstrating lambdas and streams with an array of
Integer
s. (Part 1 of 2.)
