How to Split a String into Equal Length Substrings in Java?

It is common practice in Java to split strings into smaller strings of equal length to process larger strings into usable substrings. We can do this with the substring method of the loop. This method extracts a substring of the specified length from the input string and stores it in a list.

Example to Split String into Equal Length Substrings

Input: "Hello, World!", length = 5
Output: "Hello", ", Wor", "ld!"

Input: "GeeksforGeeks", length = 4
Output: "Geek", "sfor", "Geek", "s"

Method to Split a String into equal-length Substrings in Java

In Java, to split a string into substrings of equal length, we can use the substring method in a loop,

• First, we need to determine the desired length of substring.
• Then, remove the substring of the specified length and reconnect the original string.
• At last, use the substring() method to get a substring from the current index to the next index (based on the length) at each iteration.

Java Program to Split a String into Equal Length Substrings

Below are the two examples to implement splitting a string into equal length substrings in Java.

Example 1: Splitting “Hello, World!” into Substrings of Length 5

Java

// Java program to Split a String into Equal Length Substrings
import java.io.*;
public class GFG 
{
    public static void main(String args[])
    {
        // Define the substring length
        int length = 5;

        // Original string
        String input = "Hello, World!";

        // Loop through the string by the substring length
        for (int i = 0; i < input.length(); i += length) 
        {
            // Extract the substring from the current index to
            // the next substring length
            String sub = input.substring(
                i, Math.min(i + length, input.length()));
            
            System.out.println(sub);
        }
    }
}

Output

Hello
, Wor
ld!

Complexity of the above method:

Time Complexity: O(n), here n is the length of the original string.
Auxiliary Space: O(n)

Example 2: Splitting “GeeksforGeeks” into Substrings of Length 4

Java

import java.io.*;
public class GFG {
    public static void main(String args[])
    {
        // Define the substring length
        int length = 4;

        // Original string
        String input = "GeeksforGeeks";

        // Loop through the string by the substring length
        for (int i = 0; i < input.length(); i += length) {
            // Extract the substring from the current index to
            // the next substring length
            String sub = input.substring(
                i, Math.min(i + length, input.length()));
            
            System.out.println(sub);
        }
    }
}

Output

Geek
sfor
Geek
s

Complexity of the above method:

Time Complexity: O(n), here n is the length of the original string.
Auxiliary Space: O(n)

Example 3: Using Custom Method

We can create a custom method to split a string into substrings of equal length without relying on external libraries. This method involves iterating through the original string and extracting substrings of the desired length.

Java

public class Main {
    public static void main(String[] args) {
        // Define the substring length
        int length = 5;

        // Original string
        String input = "Hello, World!";

        // Split the string into substrings of equal length
        String[] substrings = splitString(input, length);

        // Output the substrings
        for (String sub : substrings) {
            System.out.println(sub);
        }
    }

    // Custom method to split a string into substrings of equal length
    public static String[] splitString(String input, int length) {
        int numOfSubstrings = (int) Math.ceil((double) input.length() / length);
        String[] substrings = new String[numOfSubstrings];
        
        for (int i = 0; i < numOfSubstrings; i++) {
            int start = i * length;
            int end = Math.min(start + length, input.length());
            substrings[i] = input.substring(start, end);
        }
        
        return substrings;
    }
}

Output

Hello
, Wor
ld!

Complexity of the above method:

Time Complexity: O(n), where n is the length of the original string.
Auxiliary Space: O(n)