用String.format（）方法格式化輸出 或 拼接字串實現

exa:
實現格式化時間，此方法有三個int型引數，
輸出類似09:03:12的時間格式
中間需要判斷輸入的數字是否符合實際情況，
比如小時數就不能大於24，如果大於24就提示輸入錯誤。

public static void main(String[] args) {
        Scanner cin = new Scanner(System.in);
        int hour = 0, minute = 0, second = 0;
        // 字串拼接方式實現格式化輸出
        String hours = ""
 
, minutes = "", seconds = "";
        lable1: {
            while (true) {
                do {
                    System.out.println("輸入“-1” 退出迴圈測試\n請輸入小時數：");
                    hour = cin.nextInt();
                    if (hour == -1) {
                        break lable1;
                    }
                    if
 
 (hour < 0 || hour > 24) {
                        System.out.println("輸入的小時數不在範圍內！請重新輸入！");
                    }
                } while (hour > 24 || hour < 0);

                if (hour >= 0 && hour < 10) {
                    hours = "0" + hour;
                } else {
                    hours = hour + ""
 
;
                }
                do {
                    System.out.println("請輸入分鐘數：");
                    minute = cin.nextInt();
                    if (minute < 0 || minute > 60) {
                        System.out.println("輸入的分鐘數不在範圍內！請重新輸入！");
                    }
                } while (minute > 60 || minute < 0);
                if (minute >= 0 && minute < 10) {
                    minutes = "0" + minute;
                } else {
                    minutes = minute + "";
                }
                do {
                    System.out.println("請輸入秒數：");
                    second = cin.nextInt();
                    if (second < 0 || second > 60) {
                        System.out.println("輸入的秒數不在範圍內！請重新輸入！");
                    }
                    if (second >= 0 && second < 10) {
                        seconds = "0" + second;
                    } else {
                        seconds = second + "";
                    }
                } while (second > 60 || second < 0);
                System.out.println("根據輸入轉換後的時間為： " + hours + ":" + minutes
                        + ":" + seconds + "\n");
System.out.println("----------------------------------");


    // 方式二 凋用String.format()方法進行格式化
                hours = String.format("%02d", hour);
                minutes = String.format("%02d", minute);
                seconds = String.format("%02d", second);
            System.out.println("根據輸入轉換後的時間為:" +                hours + ":" + minutes + ":"  + seconds);
            }
        }
    }