Java: Find the longest substring appears at both ends of a given string

Last update on May 21 2025 12:50:08 (UTC/GMT +8 hours)

93. Longest Prefix and Suffix Substring

Write a Java program to find the longest substring that appears at both ends of a given string.

Visual Presentation:

Sample Solution:

Java Code:

import java.util.*;

// Define a class named Main
public class Main {

  // Method to find the longest substring that appears at both ends of the given string
  public String appearInBothEnds(String stng) {
    int l = stng.length(); // Get the length of the given string
    String f_str = ""; // Initialize a string to store the found substring
    String tmp = ""; // Initialize a temporary string

    // Loop through the characters of the given string
    for (int i = 0; i < l; i++) {
      tmp += stng.charAt(i); // Add the current character to the temporary string
      int t_len = tmp.length(); // Get the length of the temporary string

      // Check if the temporary string is present both at the beginning and end of the main string
      if (i < l / 2 && tmp.equals(stng.substring(l - t_len, l))) {
        f_str = tmp; // Update the found substring if a match is found
      }
    }
    return f_str; // Return the longest substring appearing at both ends of the string
  }

  // Main method to execute the program
  public static void main(String[] args) {
    Main m = new Main(); // Create an instance of the Main class

    String str1 = "playersplay"; // Given string
    // Display the given string and the longest substring appearing at both ends
    System.out.println("The given string is: " + str1);
    System.out.println("The longest substring in the string is: " + m.appearInBothEnds(str1));
  }
}

Sample Output:

The given string is: playersplay
The longest substring in the string is: play

Flowchart:

For more Practice: Solve these Related Problems:

• Write a Java program to identify the longest substring that is both a prefix and a suffix of a given string.
• Write a Java program to find and return the maximum length border substring in a string.
• Write a Java program to compute the longest common prefix and suffix of a string.
• Write a Java program to determine the longest substring that occurs at both the beginning and the end of the input.

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