将字符串转化为字符数组,再进行循环比较判断

import java.util.*;
import java.io.*;
public class Main {

    public static void main(String[] args) throws Exception{
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
        String str = "";
        while ((str = bufferedReader.readLine()) != null) {
            int number = 0;
            char[] chars = str.toCharArray();
            for (char item : chars) {
                if (item >= 'A' && item <= 'Z') {
                    number++;
                }
            }
            System.out.println(number);
        }
    }
}