Duplicate characters with count from string using loop

Following is the logic:

• Take one character from string.
• Compare this character with other characters of the string.
• If character is found then this is a duplicate character and increase counter of that character.
• Remove this character from string so that it is not picked in next iteration.

public class DuplicateCharsWithCount {

	public static void main(String[] args) {
		findDuplicateCharsWithCount("Hello from Learnitweb");
	}

	private static void findDuplicateCharsWithCount(String str) {
		int count;
		for (int i = 0; i < str.length(); i++) {
			count = 1;
			// Take one char at a time
			char c = str.charAt(i);
			// Don't count spaces
			if (c == ' ')
				continue;
			for (int j = i + 1; j < str.length(); j++) {
				if (c == str.charAt(j)) {
					count++;
					// remove the char so that it is not picked again in next iteration
					str = str.substring(0, j) + str.substring(j + 1);
				}
			}
			if (count > 1) {
				System.out.println(c + ":" + count);
			}
		}
	}
}

Output

e:3
l:2
o:2
r:2

Duplicate characters with count from string using map

Following is the logic:

1. Create character array from string.
2. Create a empty map.
3. Loop array and take one character at a time. Check for each character in map.
4. Check if the character is found as key in map. If character is not found then put character as key in map and value as 1.
5. If character is found then increase value of the key(character) by 1.

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

public class DuplicateCharsWithCount {

	public static void main(String[] args) {
		String str = "Hello from Learnitweb";
		char[] chars = str.toCharArray();

		Map<Character, Integer> map = new HashMap<>();
		for (char c : chars) {
			if (map.containsKey(c)) {
				int counter = map.get(c);
				map.put(c, ++counter);
			} else {
				map.put(c, 1);
			}
		}

		System.out.println("Duplicate characters:");
		
		for (char c : map.keySet()) {
			if (map.get(c) > 1) {
				//Do not print space
				if(c != ' ') {
					System.out.println(c + ":" + map.get(c));
				}
			}
		}
	}
}

Output

e:3
l:2
o:2
r:2