Split a String into fixed-length chunks in Java

This post will discuss how to split a string into fixed-length chunks in Java where the last chunk can be smaller than the specified length.

1. Using Guava

If you prefer the Guava library, you can use the Splitter class. For example, the expression Splitter.fixedLength(n).split(s) returns a splitter that divides the string s into chunks of length n.

import com.google.common.base.Splitter;

public class Main

{

public static void main(String[] args) {

String s = "ABCDEFGHIJKLMNO";

int chunkSize = 5;

Iterable<String> chunks = Splitter.fixedLength(chunkSize).split(s);

System.out.println(chunks); // [ABCDE, FGHIJ, KLMNO]

}

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2. Using `String.split()` method

The String class contains the split() method that splits a string around matches of the given regular expression. You can use it to split a string into equal size chinks. The following code uses the split() method to split a string into equal size chunks of length 5 using the regular expression (?<=\\G.{5}) that uses lookbehind.

import java.util.Arrays;

public class Main

{

public static void main(String[] args) {

String s = "ABCDEFGHIJKLMNO";

int chunkSize = 5;

String[] chunks = s.split("(?<=\\G.{" + chunkSize + "})");

System.out.println(Arrays.toString(chunks)); // [ABCDE, FGHIJ, KLMNO]

}

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3. Using `String.substring()` method

The idea is to extract each chunk using the String.substring(int, int) method to partition the string into fixed-length slices.

import java.util.ArrayList;

import java.util.List;

public class Main

{

public static List<String> split(String s, int chunkSize) {

List<String> chunks = new ArrayList<>();

for (int i = 0; i < s.length(); i += chunkSize) {

chunks.add(s.substring(i, Math.min(s.length(), i + chunkSize)));

}

return chunks;

}

public static void main(String[] args) {

String s = "ABCDEFGHIJKLMNO";

int chunkSize = 4;

System.out.println(split(s, chunkSize)); // [ABCD, EFGH, IJKL, MNO]

}

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If you use Java 8 or above, you can use Stream API. Here's the equivalent code:

import java.util.List;

import java.util.stream.Collectors;

import java.util.stream.IntStream;

public class Main

{

public static List<String> split(String s, int chunkSize) {

return IntStream.iterate(0, i -> i < s.length(), i -> i + chunkSize)

.mapToObj(i -> s.substring(i, Math.min(s.length(), i + chunkSize)))

.collect(Collectors.toList());

}

public static void main(String[] args) {

String s = "ABCDEFGHIJKLMNO";

int chunkSize = 4;

System.out.println(split(s, chunkSize)); // [ABCD, EFGH, IJKL, MNO]

}

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4. Using `Pattern.compile()` method

To split a string into fixed-length chunks, you can create a matcher to determine the indexes of the chunk. Here's how the code would look like:

import java.util.ArrayList;

import java.util.List;

import java.util.regex.Matcher;

import java.util.regex.Pattern;

public class Main

{

public static void main(String[] args) {

String s = "ABCDEFGHIJKLMNO";

int chunkSize = 5;

Matcher match = Pattern.compile(".{1," + chunkSize + "}").matcher(s);

List<String> chunks = new ArrayList<>();

while (match.find()) {

chunks.add(s.substring(match.start(), match.end()));

}

System.out.println(chunks); // [ABCDE, FGHIJ, KLMNO]

}

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That's all about splitting a string into fixed-length chunks in Java.

Split a String into fixed-length chunks in Java

1. Using Guava

2. Using String.split() method

3. Using String.substring() method

4. Using Pattern.compile() method

2. Using `String.split()` method

3. Using `String.substring()` method

4. Using `Pattern.compile()` method