In Java 8, you can either use Arrays.stream
or Stream.of
to convert an Array into a Stream.
1. Object Arrays
For object arrays, both Arrays.stream
and Stream.of
returns the same output.
package com.mkyong.java8;
import java.util.Arrays;
import java.util.stream.Stream;
public class TestJava8 {
public static void main(String[] args) {
String[] array = {"a", "b", "c", "d", "e"};
//Arrays.stream
Stream<String> stream1 = Arrays.stream(array);
stream1.forEach(x -> System.out.println(x));
//Stream.of
Stream<String> stream2 = Stream.of(array);
stream2.forEach(x -> System.out.println(x));
}
}
Output
a b c d e a b c d e
Review the JDK source code.
/**
* Returns a sequential {@link Stream} with the specified array as its
* source.
*
* @param <T> The type of the array elements
* @param array The array, assumed to be unmodified during use
* @return a {@code Stream} for the array
* @since 1.8
*/
public static <T> Stream<T> stream(T[] array) {
return stream(array, 0, array.length);
}
/**
* Returns a sequential ordered stream whose elements are the specified values.
*
* @param <T> the type of stream elements
* @param values the elements of the new stream
* @return the new stream
*/
@SafeVarargs
@SuppressWarnings("varargs") // Creating a stream from an array is safe
public static<T> Stream<T> of(T... values) {
return Arrays.stream(values);
}
For object arrays, the
Stream.of
method is calling the Arrays.stream
internally.
2. Primitive Arrays
For primitive array, the Arrays.stream
and Stream.of
will return different output.
package com.mkyong.java8;
import java.util.Arrays;
import java.util.stream.IntStream;
import java.util.stream.Stream;
public class TestJava8 {
public static void main(String[] args) {
int[] intArray = {1, 2, 3, 4, 5};
// 1. Arrays.stream -> IntStream
IntStream intStream1 = Arrays.stream(intArray);
intStream1.forEach(x -> System.out.println(x));
// 2. Stream.of -> Stream<int[]>
Stream<int[]> temp = Stream.of(intArray);
// Cant print Stream<int[]> directly, convert / flat it to IntStream
IntStream intStream2 = temp.flatMapToInt(x -> Arrays.stream(x));
intStream2.forEach(x -> System.out.println(x));
}
}
Output
1 2 3 4 5 1 2 3 4 5
Review the JDK source code.
/**
* Returns a sequential {@link IntStream} with the specified array as its
* source.
*
* @param array the array, assumed to be unmodified during use
* @return an {@code IntStream} for the array
* @since 1.8
*/
public static IntStream stream(int[] array) {
return stream(array, 0, array.length);
}
/**
* Returns a sequential {@code Stream} containing a single element.
*
* @param t the single element
* @param <T> the type of stream elements
* @return a singleton sequential stream
*/
public static<T> Stream<T> of(T t) {
return StreamSupport.stream(new Streams.StreamBuilderImpl<>(t), false);
}
For object arrays, both are calling the same
Arrays.stream
(refer example 1, JDK source code). For primitive arrays, I prefer Arrays.stream
as well, because it returns fixed size IntStream
directly, easier to manipulate it.
P.S Tested with Oracle JDK 1.8.0_77