Program to find Repeated/Duplicate Characters of String

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

    public class FindDuplicateCharacters{
        public static void main(String args[]) {
            printDuplicateCharacters("Programming");
            printDuplicateCharacters("Combination");
            printDuplicateCharacters("Java");
        }

        /* * Find all duplicate characters in a String and print each of them. */
        public static void printDuplicateCharacters(String word) {
            char[] characters = word.toCharArray();
            // build HashMap with character and number of times they appear in String 
            Map<Character, Integer> charMap = new HashMap<Character, Integer>();
            for (Character ch : characters) {
                if (charMap.containsKey(ch)) {
                    charMap.put(ch, charMap.get(ch) + 1);
                } else {
                    charMap.put(ch, 1);
                }
            }
            // Iterate through HashMap to print all duplicate characters of String 
            Set<Map.Entry<Character, Integer>> entrySet = charMap.entrySet();
            System.out.printf("List of duplicate characters in String '%s' %n", word);
            for (Map.Entry<Character, Integer> entry : entrySet) {
                if (entry.getValue() > 1) {
                    System.out.printf("%s : %d %n", entry.getKey(), entry.getValue());
                }
            }
        }
    }

List of duplicate characters in String 'Programming'
r : 2
g : 2
m : 2
List of duplicate characters in String 'Combination'
i : 2
n : 2
o : 2
List of duplicate characters in String 'Java'
a : 2

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