How do you find duplicate characters in a string?

Following program demonstrate it.

File: DuplicateCharFinder .java

import java.util.HashMap;
import java.util.Map;
import java.util.Set;
 
public class DuplicateCharFinder {
	public void findIt(String str) {
		Map<Character, Integer> baseMap = new HashMap<Character, Integer>();
		char[] charArray = str.toCharArray();
		for (Character ch : charArray) {
			if (baseMap.containsKey(ch)) {
				baseMap.put(ch, baseMap.get(ch) + 1);
			} else {
				baseMap.put(ch, 1);
			}
		}
		Set<Character> keys = baseMap.keySet();
		for (Character ch : keys) {
			if (baseMap.get(ch) > 1) {
				System.out.println(ch + "  is " + baseMap.get(ch) + " times");
			}
		}
	}
 
	public static void main(String a[]) {
		DuplicateCharFinder dcf = new DuplicateCharFinder();
		dcf.findIt("India is my country");
	}
}

Output:

   is 3 times
i  is 2 times
n  is 2 times
y  is 2 times

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Java String