题解 | #字符个数统计#

import java.util.HashSet;
import java.util.Scanner;
import java.util.Set;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        String s = in.nextLine();
        System.out.print(countDifferentChar(s));

    }
    public static int countDifferentChar(String word){
        Set<Character> set = new HashSet<>();
        int count = 0;
        for(int i=0 ; i<word.length() ; ++i){
            char c = word.charAt(i);
            if(set.contains(c)){
                continue;
            }
            else{
                ++count;
                set.add(c);
            }
        }
        return count;

    }
}