Java 8 Stream skip() Examples JavaProgramTo.com

1. Overview

In this article, You'll learn how to use stream skip() method of java 8 and how to skip the first n objects from stream.

2. Java 8 Stream skip() Syntax

skip() method is an intermediate operation that returns Stream of objects.

Stream<T> skip(long n)

This method returns a stream consisting of the remaining elements of this stream after discarding the first n elements of the stream. If this stream contains fewer than n elements then an empty stream will be returned.

skip() method takes a long parameter and returns Stream.

3. Java 8 Stream skip() Method

You've to remember the following points before using the skip() method.

A) skip() method is a stateful intermediate operation similar to the sorted(), filter() methods.

B) Returns a Stream after discarding first n elements from the stream.

C) If the stream has less than the number n given, it returns an empty sequential stream by calling the Stream.empty() method.

D) This is good for only sequential streams and must avoid in parallel streams for higher values of n.

E) If you use unordered infinite streams or unordered() streams may result in producing better results.

F) It just skips the first n values from the stream that the order is present in the underlying base stream or previous intermediate operation call output.

G) n value can not be negative. If n is negative, it throws java.lang.IllegalArgumentException.

4. Java 8 Stream skip() Example 1

Understand the skip() example program to skip the first 10 numbers from infinite numbers series and collect the next 20 values using limit() method.

If you are using infinite streams then you must have to use the limit() method. Otherwise, stream will end up in memory-related issues.

package com.javaprogramto.java8.skip;

import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;

public class Skip10ValuesExample {
    public static void main(String[] args) {

        Stream<Integer> numnerSeries = Stream.iterate(1, i -> i+ 1);

        List<Integer> next20Numbers = numnerSeries.skip(10).limit(20).collect(Collectors.toList());

        System.out.println("20 Numbers after skipping first 10 numbers");
        next20Numbers.forEach(number -> System.out.println(number));
    }
}

Output:

20 Numbers after skipping first 10 numbers
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30

5. Java 8 Stream skip() Example 2

Example to skip the first 5 even numbers from List.

import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;

public class Skip5EvenNumbersExample {
    public static void main(String[] args) {

        Stream<Integer> evenNumbers = Stream.of(2, 4, 5, 8, 10, 12, 14, 16, 18, 20);

        List<Integer> next20Numbers = evenNumbers
                .skip(5)
                .collect(Collectors.toList());

        System.out.println("skipping first 5 even Numbers");
        next20Numbers.forEach(number -> System.out.println(number));
    }
}

Output:

skipping first 5 even Numbers
12
14
16
18
20

6. Java 8 Stream skip() Example 3

What is the output if a negative index is passed to skip() method.

public class SkipNegativeIndexExample {
    public static void main(String[] args) {

        Stream<Integer> numbers = Stream.of(1, 2, 3);

        List<Integer> expectingError = numbers
                .skip(-25)
                .collect(Collectors.toList());

        System.out.println("skipping first 5 even Numbers");
        expectingError.forEach(number -> System.out.println(number));
    }
}

Output:

Exception in thread "main" java.lang.IllegalArgumentException: -25
	at java.base/java.util.stream.ReferencePipeline.skip(ReferencePipeline.java:476)
	at com.javaprogramto.java8.skip.SkipNegativeIndexExample.main(SkipNegativeIndexExample.java:13)