题解 | #字符个数统计#

利用Set去重的特性，以及流操作来过滤

import java.util.*;
import java.util.stream.Collectors;

public class Main {

        public static void main(String[] args){
            Scanner s = new Scanner(System.in);
            HashSet<Character> set = new HashSet<>();
            String line = s.nextLine();
            char[] chars = line.toCharArray();
            for (char aChar : chars) {
                set.add(aChar);
            }
            set.stream().filter(c -> Integer.valueOf(c) >= 0 && Integer.valueOf(c) <= 127).collect(Collectors.toSet());
            System.out.println(set.size());
        }
}