Java基础String类-统计大小写和数字字符

public class HomeworkTest01 {
    public static void main(String[] args) {
        String s = "ABCDefgsji1234hjizsdlhniknHGD4789VVHBUmcihsnjv";
        int upper = 0;
        int lower = 0;
        int num = 0;
        for(int i = 0;i<s.length();i++){
            char c = s.charAt(i);
            if(c>='A' && c<='Z'){
                upper++;
            }
            if(c>='a' && c<='z'){
                lower++;
            }
            if(c>='0' && c<='9'){
                num++;
            }
        }
        System.out.println("大写字符出现的次数为"+upper+"次，小写字符出现的次数为"+lower+"次，数字出现的的次数为"+num+"次");
    }
}