Java Program to check for Duplicate Characters

Program

import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import java.util.Scanner;
public class DuplicateCharactersCheck {
  public void countDuplicateChar(String string){ 
    Map<Character, Integer> countMap = new HashMap<Character, Integer>(); 
    char[] characters = string.toCharArray(); 
    for(Character ch:characters){
      if(countMap.containsKey(ch)){
         countMap.put(ch, countMap.get(ch)+1);
      } else {
         countMap.put(ch, 1);
        }
    }
    Set<Character> keys = countMap.keySet(); 
    for(Character ch:keys){    
        if(countMap.get(ch) > 1) {
            System.out.println(ch+" "+countMap.get(ch));     
        } 
        else{
          System.out.println("No Duplicate characters present");  
        }     
    }
  }
  public static void main(String[] args){
    DuplicateCharactersCheck duplicateCharactersCheck = new DuplicateCharactersCheck();
    System.out.println("Example String 1: www.oodlescoop.com");   
    duplicateCharactersCheck.countDuplicateChar("www.oodlescoop.com");
    System.out.println("\nExample String 2: Engineering");   
    duplicateCharactersCheck.countDuplicateChar("Engineering"); 
    Scanner reader = new Scanner(System.in);
    System.out.println("Enter a string: ");
    String enteredString = reader.next();
    System.out.println("Duplicate Count for string : "+ enteredString +" is: ");
    duplicateCharactersCheck.countDuplicateChar(enteredString); 
    }
}

Output

$ javac DuplicateCharactersCheck.java
$ java DuplicateCharactersCheck
Example String 1: www.oodlescoop.com
c 2
w 3
. 2
o 5
Example String 2: Engineering
e 2
g 2
i 2
n 3
Enter a string:
Programming
Duplicate Count for string : Programming is:
r 2
g 2
m 2