Java Program to find duplicate characters count in a string - The Coding Shala

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 In this post, we will learn how to find duplicate characters count in a string and will write a Java program to find duplicate characters and their count.

Java Program to find duplicate characters count in a String


A string is given, you have to find all the duplicate characters in the string and need to return their count.

Example 1

Input: "aabb"
Output: a 2
             b 2

Approach 1

We need to count the occurrence of each character in the given string. If the count is more than 1(one) then it's a duplicate character and we need to return that.

Java Program: 

import java.util.*;

class Main {
	public static void duplicate(String str) {
		 int[] arr = new int[26];   
		 for(int i=0; i<str.length(); i++) {
			int index = str.charAt(i) - 'a';
			arr[index] = arr[index]+1;
		 for(int i=0; i<26; i++){
			if(arr[i] > 1){
				char c = (char)(i + 'a');
				System.out.println("duplicate char "+c+" count is "+arr[i]); 
	public static void main(String[] args) {
			String s1 = "abcdaefghccabcda";

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