Java Stream skip()

Stream skip(n) method is used to skip the first 'n' elements from the given Stream.

The skip() method returns a new Stream consisting of the remaining elements of the original Stream, after the specified n elements have been discarded in the encounter order.

1. Stream skip() Method

1.1. Method Syntax

Stream<T> skip(long n)

The n is the number of leading elements to be discarded. It returns a new Stream consisting of elements picked from the original stream.

The method may throw IllegalArgumentException if n is negative.

1.2. Description

  • Stream skip() method is stateful intermediate operation. Stateful operations, such as distinct and sorted, may incorporate state from previously seen elements when processing new elements.
  • Returns a stream consisting of the remaining elements of the stream after discarding the first n elements of the stream.
  • If the stream contains fewer than n elements then an empty stream will be returned.
  • Generally skip() is a cheap operation, it can be quite expensive on ordered parallel pipelines, especially for large values of n.
  • Using an unordered stream source (such as generate(Supplier)) or removing the ordering constraint with BaseStream.unordered() may result in significant speedups of skip() in parallel pipelines.
  • skip() skips the first n elements in the encounter order.

2. Stream skip() Example

In this Java program, we are using the skip() method to skip the first 5 even numbers from an infinite stream of even numbers and then collect the next 10 even numbers into a new Stream.

Stream<Integer> evenNumInfiniteStream = Stream.iterate(0, n -> n + 2);

List<Integer> newList = evenNumInfiniteStream
		.skip(5)
		.limit(10)
		.collect(Collectors.toList());
		
System.out.println(newList);

Program output.

[10, 12, 14, 16, 18, 20, 22, 24, 26, 28]

3. Conclusion

The Stream skip() method can be useful in certain cases where we need to get the elements from a Stream but first, we need to skip a few elements from the Stream.

The fact, that skip() returns the elements in the encounter order, makes it very useful for normal business usecases as well.

Happy Learning !!

Sourcecode on Github

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HowToDoInJava

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