public class TestSubstring {
    public static void main(String[] args) {     
        String s = getConvert("adsJKJ3K21AfaAD134F13241d134134s141faAAFDF");
        System.out.println(s);
      
    }

    //將一個字符串中的首字母轉換成大寫，其它的全部轉換成小寫
    public static String getConvert(String str) {
        String first = str.substring(0, 1);
        String after = str.substring(1); //substring(1),獲取索引位置1后面所有剩余的字符串
        first = first.toUpperCase();
        after = after.toLowerCase();
        return "轉換后的字符串:" + first + after;
    }
}