Find and Print all duplicate characters in given string | Java example

Java program for find all duplicate characters in given String 

Or

Java program to display only repeated letters in a integer string

Solution 1 :-

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

public class StreamApi {

    public static void main(String[] args) {
       
        Scanner sc = new Scanner(System.in);
        System.out.println("Enter String");
        String str = sc.nextLine();
       
        char[] charArray = str.toCharArray();
       
        Map<Character, Integer> map = new HashMap<>();
        for (char c : charArray) {
            if (!map.containsKey(c)) {
                map.put(c, 1);
            } else {
                map.put(c, map.get(c)+1);
            }
        }
       
        for (Entry<Character, Integer> c : map.entrySet()) {
            if (c.getValue() > 1) {
                System.out.println(c.getKey());
            }
        }
    }
}

Output :-
Enter String
aabbccd
a
b
c
_________

Enter String
abcdaefg
a
_________

Enter String
programming blog
r
g
m
o

Explanation :-

• Using scanner class we take input from user.
• After we convert string to character array using toCharArray() method.
• For loop through character array and put character as key and count of occurrence that specific character as value.
• After for loop, we loop through map and check all duplicates characters and print them one by one.