机试题：检索一个字符串中有多少种字符

检索字符的种类

package com.swun.se;
import java.util.*;

public class TestDemo{
    public static void main(String args[])throws Exception{
      String str = "abcdeffffffffffffffffffff"; 
      char[] arr = str.toCharArray(); 
       int kinds = TestDemo.countKinds(arr);
      System.out.println("有"+kinds+"种字符");
      
    }
    public static int countKinds(char[] args){
      Set<Character> set = new HashSet<>();
      for(int i=0;i<args.length;i++){
          set.add(args[i]);
      }
       return set.size(); 
        
      
  }

  
}