String類練習統計一個字符串中大小寫字母及數字字符個數

public class StringPractice {
    public static void main(String[] args) {
        //創建一個文本掃描器
        Scanner sc = new Scanner(System.in);
        System.out.println("請輸入一個字符串：");
        String str = sc.next();

        //定義三個變量用來統計大寫字母，小寫字母，數字的個數
        int bigCount = 0;
        int smallCount = 0;
        int numCount = 0;

        //遍歷字符串，對每個字符進行判斷
        for (int i = 0;i<str.length();i++){
            char chs = str.charAt(i);
            //如果
            if (chs >= 'A' && chs <= 'Z'){
                bigCount++;
            }else if (chs >= 'a' && chs <= 'z'){
                smallCount++;
            }else if (chs >= '0' && chs <= '9'){
                numCount++;
            }else {
                System.out.println("該字符"+chs+"非法");
            }
        }
        //輸出結果
        System.out.println("大寫字符："+bigCount+"個");
        System.out.println("小寫字符："+smallCount+"個");
        System.out.println("數字字符："+numCount+"個");


    }
}