strings.java

import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

public class DistinctCharsCount {

	public static void main(String[] args) {

		printDistinctCharsWithCount("abc");
		printDistinctCharsWithCount("abcab3");
		printDistinctCharsWithCount("hi there, i am pankaj");
	}

	private static void printDistinctCharsWithCount(String input) {
		Map<Character, Integer> charsWithCountMap = new HashMap<>();

		// using Map merge method from Java 8
		for (char c : input.toCharArray())
			charsWithCountMap.merge(c, 1, Integer::sum);
		System.out.println(charsWithCountMap);

		// another way using latest Java enhancements and no for loop, a bit complex though
		List<Character> list = input.chars().mapToObj(c -> (char) c).collect(Collectors.toList());

		list.stream().forEach(c -> charsWithCountMap.merge(c, 1, Integer::sum));

		System.out.println(charsWithCountMap);

	}

}