Get a slice from a List in Java

This post will discuss how to get a slice (or a sub-list) from a List in Java.

1. Using `list.subList()` method

You can use the List.sublist() method to get a view of the portion of this list between the specified range of indices.

import java.util.List;

import java.util.stream.Collectors;

import java.util.stream.IntStream;

class Main

{

public static void main(String[] args)

{

List<Character> chars = IntStream.rangeClosed(65, 90)

.mapToObj(x -> (char)x)

.collect(Collectors.toList());

int startIndex = 3;

int endIndex = 5;

List<Character> sublist = chars.subList(startIndex, endIndex + 1);

System.out.println(sublist);

}

Download Run Code

Output:

[D, E, F]

Note that the sublist returned by the subList() method is backed by the original list, any non-structural changes in the sublist are reflected in the original list and vice-versa. If you want to avoid this behavior, it is advisable to wrap the list using the ArrayList constructor. For instance,

import java.util.ArrayList;

import java.util.List;

import java.util.stream.Collectors;

import java.util.stream.IntStream;

class Main

{

public static void main(String[] args)

{

List<Character> chars = IntStream.rangeClosed(65, 90)

.mapToObj(x -> (char)x)

.collect(Collectors.toList());

List<Character> sublist = new ArrayList<>(chars.subList(5, 6));

System.out.println(sublist);

}

Download Run Code

Output:

[D, E, F]

2. Using Stream API

The idea here is to get the stream of the elements in the list and call the skip(n) method to skip the first n elements. Then call the limit(k) method to return a new stream consisting of the next k elements in the encounter order and collect the stream to a new list.

This process generates the sublist of the original list in the range [n, n + k].

import java.util.List;

import java.util.stream.Collectors;

import java.util.stream.IntStream;

class Main

{

public static<T> List<T> getSubList(List<T> list, int startIndex, int endIndex) {

return list.stream()

.skip(startIndex)

.limit(endIndex - startIndex + 1)

.collect(Collectors.toList());

}

public static void main(String[] args)

{

List<Character> chars = IntStream.rangeClosed(65, 90)

.mapToObj(x -> (char)x)

.collect(Collectors.toList());

int startIndex = 3;

int endIndex = 5;

List<Character> sublist = getSubList(chars, startIndex, endIndex);

System.out.println(sublist);

}

Download Run Code

Output:

[D, E, F]

3. Using Enhanced For loop

Here’s a version without streams using an enhanced for loop (self-explanatory):

import java.util.ArrayList;

import java.util.List;

import java.util.stream.Collectors;

import java.util.stream.IntStream;

class Main

{

public static<T> List<T> getSubList(List<T> list, int startIndex, int endIndex) {

List<T> sublist = new ArrayList<>();

long index = 0;

for (T e : list) {

if (index >= startIndex && index <= endIndex) {

sublist.add(e);

} else if (index > endIndex) {

break;

}

index++;

}

return sublist;

}

public static void main(String[] args)

{

List<Character> chars = IntStream.rangeClosed(65, 90)

.mapToObj(x -> (char)x)

.collect(Collectors.toList());

int startIndex = 3;

int endIndex = 5;

List<Character> sublist = getSubList(chars, startIndex, endIndex);

System.out.println(sublist);

}

Download Run Code

Output:

[D, E, F]

The code can be simplified using a regular for loop, as shown below:

import java.util.ArrayList;

import java.util.List;

import java.util.stream.Collectors;

import java.util.stream.IntStream;

class Main

{

public static<T> List<T> getSubList(List<T> list, int startIndex, int endIndex) {

List<T> sublist = new ArrayList<>();

for (int i = startIndex; i <= Integer.min(endIndex, list.size()); i++) {

sublist.add(list.get(i));

}

return sublist;

}

public static void main(String[] args)

{

List<Character> chars = IntStream.rangeClosed(65, 90)

.mapToObj(x -> (char)x)

.collect(Collectors.toList());

int startIndex = 3;

int endIndex = 5;

List<Character> sublist = getSubList(chars, startIndex, endIndex);

System.out.println(sublist);

}

Download Run Code

Output:

[D, E, F]

That’s all about getting a slice from a List in Java.

Get a slice from a List in Java

1. Using list.subList() method

2. Using Stream API

3. Using Enhanced For loop

1. Using `list.subList()` method