Java Reference
In-Depth Information
How would you generate an infinite stream of a repeating value? For example, how would you generate an
infinite stream of zeroes? The following snippet of code shows you how to do this:
IntStream zeroes = IntStream.generate(() -> 0);
Streams from Arrays
The
Arrays
class in the
java.util
package contains an overloaded
stream()
static method to create sequential
streams from arrays. You can use it to create an
IntStream
from an
int
array, a
LongStream
from a
long
array, a
DoubleStream
from a
double
array, and a
Stream<T>
from an array of the reference type
T
. The following snippet of
code creates an
IntStream
and a
Stream<String>
from an
int
array and a
String
array:
// Creates a stream from an int array with elements 1, 2, and 3
IntStream numbers = Arrays.stream(new int[]{1, 2, 3});
// Creates a stream from a String array with elements "Ken", and "Jeff"
Stream<String> names = Arrays.stream(new String[] {"Ken", "Jeff"});
■
You can create a stream from a reference type array using two methods:
Arrays.stream(T[] t)
and
Stream.of(T...t)
method. providing two methods in the library to accomplish the same thing is intentional.
Tip
Streams from Collections
The
Collection
interface contains the
stream()
and
parallelStream()
methods that create sequential and parallel
streams from a
Collection
, respectively. The following snippet of code creates streams from a set of strings:
import java.util.HashSet;
import java.util.Set;
import java.util.stream.Stream;
...
// Create and populate a set of strings
Set<String> names = new HashSet<>();
names.add("Ken");
names.add("jeff");
// Create a sequential stream from the set
Stream<String> sequentialStream = names.stream();
// Create a parallel stream from the set
Stream<String> parallelStream = names.parallelStream();
Streams from Files
Java 8 has added many methods to the classes in the
java.io
and
java.nio.file
packages to support I/O operations
using streams. For example,
•
You can read text from a file as a stream of strings in which each element represents one line of
text from the file.
JarEntry
from a
JarFile
.
•
You can obtain a stream of
