In this post, we will discuss various methods to convert array to Stream in Java 8.
1. Convert Boxed Array to Stream –
A Stream can be constructed from a boxed array using one of below methods:
1.1. Using Arrays.stream()
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// Generic function to convert array to Stream in Java 8 public static <T> Stream<T> getStream(T[] arr) { return Arrays.stream(arr); } |
1.2. Using Stream.of()
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// Generic function to convert array to Stream in Java 8 public static <T> Stream<T> getStream(T[] arr) { // Stream.of() internally uses Arrays.stream() return Stream.of(arr); } |
1.3. List.stream()
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// Generic function to convert array to Stream in Java 8 public static <T> Stream<T> getStream(T[] arr) { return Arrays.asList(arr).stream(); } |
2. Convert Primitive Array to Stream –
When we convert primitive array to Stream, we will get primitive Streams like IntStream, DoubleStream and LongStream. These primitive streams can be obtained by using one of below methods:
2.1. Using Arrays.stream()
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// Generic function to convert array to Stream in Java 8 public static IntStream getStream(int[] arr) { return Arrays.stream(arr); } |
2.2. Using IntStream.of()
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// Generic function to convert array to Stream in Java 8 public static IntStream getStream(int[] arr) { return IntStream.of(arr); } |
Note – Arrays.asList(arr).stream() and Stream.of(arr) will return Stream<int[]> not IntStream.
3. Filter Array using Stream –
We can also filter an array to match a certain criteria using Streams as shown below:
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import java.util.Arrays; import java.util.stream.Stream; class ArrayToStream { // Program to convert array to Stream and filter it public static void main(String[] args) { String[] arr = { "NYC", "Mexico", "Beijing", "New Delhi", "Tokyo" }; Stream<String> stream = Arrays.asList(arr).stream(); stream.filter(s -> s.startsWith("N")) .forEach(System.out::println); } } |
Output:
NYC
New Delhi
4. Convert Stream back to Array –
Many times we might have a Stream of elements and we want to convert it back to the array. We can easily do so as shown below:
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import java.util.Arrays; import java.util.stream.Collectors; import java.util.stream.Stream; class StreamToArray { // Program to convert Stream to an array public static void main(String[] args) { Stream<String> stream = Stream.of("NYC", "Mexico", "Beijing", "New Delhi", "Tokyo"); String[] str = stream.collect(Collectors.toList()) .toArray(new String[0]); System.out.println(Arrays.toString(str)); } } |
Output:
[NYC, Mexico, Beijing, New Delhi, Tokyo]
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