What is the forEachOrdered() method of the Stream Interface?
The forEachOrdered method is used to loop through all the elements of the stream and perform a Consumer
For example, the stream created from list is ordered, so the forEachOrdered will apply the Consumer operation on the elements in the element order present in the stream.
The forEachOrdered method doesn’t return anything; it is a terminal operation.
The Consumer operation is executed on the element before we apply the Consumer operation on the subsequent element. However, the operation can be performed by any thread, selected by the library.
Syntax
void forEachOrdered(Consumer<? super T> action)
Example
import java.util.stream.Stream;class forEachOrdered {public static void main( String args[] ) {Stream<Integer> stream = Stream.of(1,2,3,4,5);stream.forEachOrdered((number) ->{System.out.println(number * 2);});}}
In the code above, we used the Stream.of method to create a stream of numbers.
Then, we called the forEachOrdered method on the stream of numbers with the consumer operation to print each number multiplied by 2. The forEachOrdered will loop through elements in the encounter order and print the multiple of 2 of each element on the stream.
Use forEachOrdered on parallel stream
If the stream is parallel, then the Java runtime will split the stream into multiple substreams. Aggregate operations iterate over and process these substreams in parallel, and then combine the results.
When we use forEachOrdered, the elements are looped in the encounter order if the stream has a defined encounter order.
But when we use forEach on the parallelStream, the elements are not looped in encounter order, even if the stream has a defined encounter order.
import java.util.stream.Stream;import java.util.List;import java.util.Arrays;class forEachOrdered {public static void main( String args[] ) {List<Integer> list = Arrays.asList(1, 2, 3, 4);Stream<Integer> parallelStream = list.parallelStream();System.out.println("Using forEachOrdered");parallelStream.forEachOrdered((number) ->{System.out.print(number+ " ");});System.out.println();System.out.println("Using forEach");parallelStream = list.parallelStream();parallelStream.forEach((number) ->{System.out.print(number + " ");});}}
In the code above, we have:
-
Created a List of numbers with the
Arrays.asList()method, which will return aListfrom the arguments passed. -
Created the parallel stream of the
Listwith theparallelStream()method. -
Called the
forEachOrderedmethod on the parallel stream, which will iterate all the elements of the parallel stream in the encounter order. -
Called the
forEachmethod on the parallel stream, which will iterate all the elements of the parallel stream in any order.
