Java: Find the second most frequent character in a given string

Last update on May 21 2025 12:49:18 (UTC/GMT +8 hours)

34. Second Most Frequent Character

Write a Java program to find the second most frequent character in a given string.

Visual Presentation:

Sample Solution:

Java Code:

// Import necessary Java utilities.
import java.util.*;

// Define a class named Main.
public class Main {
    // Define a constant representing the number of characters (ASCII).
    static final int NOOFCHARS = 256;

    // Define a method to find the second most frequent character in a string.
    static char get2ndMostFreq(String str1) {
        // Create an array to count occurrences of each character in the string.
        int[] ctr = new int[NOOFCHARS];
        int i;

        // Count occurrences of each character in the string.
        for (i = 0; i < str1.length(); i++) {
            (ctr[str1.charAt(i)])++;
        }

        // Variables to store indices of the first and second most frequent characters.
        int ctr_first = 0, ctr_second = 0;
        for (i = 0; i < NOOFCHARS; i++) {
            if (ctr[i] > ctr[ctr_first]) {
                ctr_second = ctr_first;
                ctr_first = i;
            } else if (ctr[i] > ctr[ctr_second] && ctr[i] != ctr[ctr_first]) {
                ctr_second = i;
            }
        }

        // Return the second most frequent character.
        return (char) ctr_second;
    }

    // The main method to execute the code.
    public static void main(String args[]) {
        // Define the input string.
        String str1 = "successes";
        System.out.println("The given string is: " + str1);

        // Get the second most frequent character from the input string.
        char res = get2ndMostFreq(str1);

        // Display the result.
        if (res != '\0') {
            System.out.println("The second most frequent char in the string is: " + res);
        } else {
            System.out.println("No second most frequent character found in the string.");
        }
    }
}

Sample Output:

The given string is: successes
The second most frequent char in the string is: c

Flowchart:

For more Practice: Solve these Related Problems:

• Write a Java program to find the second most frequent character in a string, ignoring case.
• Write a Java program to determine the two most frequent characters in a string and print them in order.
• Write a Java program to identify the second most frequent character in a string using a HashMap.
• Write a Java program to find the second most frequent alphanumeric character in a string after filtering out special characters.

Go to:

• Java String Exercises Home ↩
• Java Exercises Home ↩

PREV : All Interleavings of Strings.
NEXT : String Permutations with Repetition.

Java Code Editor:

Improve this sample solution and post your code through Disqus