How To Find Out Duplicate Characters In a String Java Program

Java Program:

Write a program to find out duplicate characters in a string?

Description:

Write a program to find out duplicate or repeated characters in a
string, and calculate the count of repeatation.

Code:

package com.java2novice.algos;

import java.util.HashMap;
import java.util.Map;
import java.util.Set;

public class DuplicateCharsInString {

    public void findDuplicateChars(String str){
        
        Map<Character, Integer> dupMap = new HashMap<Character, Integer>();
        char[] chrs = str.toCharArray();
        for(Character ch:chrs){
            if(dupMap.containsKey(ch)){
                dupMap.put(ch, dupMap.get(ch)+1);
            } else {
                dupMap.put(ch, 1);
            }
        }
        Set<Character> keys = dupMap.keySet();
        for(Character ch:keys){
            if(dupMap.get(ch) > 1){
                System.out.println(ch+"--->"+dupMap.get(ch));
            }
        }
    }
    
    public static void main(String a[]){
        DuplicateCharsInString dcs = new DuplicateCharsInString();
        dcs.findDuplicateChars("Java2Novice");
    }
}

Output:

v--->2
a--->2

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