Detect Duplicate Characters in a String: Java Program Guide

In the realm of programming, simplicity often yields the most elegant solutions. When it comes to Java programming, a language known for its readability and versatility, finding duplicate characters in a string can be achieved with a straightforward approach. In this article, we’ll delve into a simple Java code snippet that helps you identify and understand duplicate characters within a given string. By the end of this article, you’ll have a solid grasp of the process and be well-equipped to tackle similar challenges in your coding journey.

Introduction to Duplicate Characters

Duplicate characters within a string refer to the occurrence of a specific character more than once. Detecting these duplicates is a fundamental task in programming, often required for data validation, manipulation, and analysis.

The Algorithm Overview

At its core, the algorithm we’ll discuss involves iterating through the characters of a given string and recording their occurrences. By using a data structure to store character counts, we can then identify characters with counts greater than one, indicating duplicates.

How to print duplicate character in given String by using scanner class ?

public class duplicate {
public static void main(String agrs[])
String str= "Helllo";
char[] carray = str.tocharArray();
System.out.println("Enter a String"+str);
System.out.println("duplicate character is in above string:");
for (int i = 0; i < str.length(); i++) {
         for (int j = i + 1; j < str.length(); j++) {
            if (carray[i] == carray[j]) {
               System.out.print(carray[j] + " ");

//Output : string is Hello
//duplicate character is in above string l

Real-world Applications

The ability to identify duplicate characters finds use in various scenarios. It aids in data cleansing, ensuring input validity, and enhancing the efficiency of certain algorithms that operate on strings.


In the realm of Java programming, simplicity often leads to powerful solutions. With the code snippet provided, you can now effortlessly identify duplicate characters within a given string. This fundamental skill will undoubtedly prove invaluable in your programming endeavors.