使用 Calendar 計算時間

一. 類型轉換

1.1 Date → Calendar

public Calendar date2Calendar(Date date){
    Calendar calendar = Calendar.getInstance();
    calendar.setTime(date);
    return calendar;
}

1.2 Calendar → Date

public Date calendar2Date(Calendar calendar){
    return calendar.getTime();
}

二. 時間計算

2.1 ?毫秒

/*
 * 計算兩個日期之間的差值：
 *      日期1：2019-12-31 12:30:12
 *      日期2：2020-01-01 13:31:13
 */
Calendar startCalendar = Calendar.getInstance();
Calendar endCalendar = Calendar.getInstance();

// 手動設置時間
startCalendar.set(2019, Calendar.DECEMBER, 31, 12, 30, 12);
endCalendar.set(2020, Calendar.JANUARY, 1, 13, 31, 13);
startCalendar.set(Calendar.MILLISECOND, 0);
endCalendar.set(Calendar.MILLISECOND, 0);

long startCalendarTimeInMills = startCalendar.getTimeInMillis();
long endCalendarTimeInMills = endCalendar.getTimeInMillis();

long differenceInMills = endCalendarTimeInMills - startCalendarTimeInMills;
System.out.println("相差：" + differenceInMills + "（毫秒）");

代碼執行結果：

相差： 90061000（毫秒）

Process finished with exit code 0

2.2 ?秒

/*
 * 計算兩個日期之間的差值：
 *      日期1：2019-12-31 12:30:12
 *      日期2：2020-01-01 13:31:13
 */
Calendar startCalendar = Calendar.getInstance();
Calendar endCalendar = Calendar.getInstance();

// 手動設置時間
startCalendar.set(2019, Calendar.DECEMBER, 31, 12, 30, 12);
endCalendar.set(2020, Calendar.JANUARY, 1, 13, 31, 13);
startCalendar.set(Calendar.MILLISECOND, 0);
endCalendar.set(Calendar.MILLISECOND, 0);

long startCalendarTimeInMills = startCalendar.getTimeInMillis();
long endCalendarTimeInMills = endCalendar.getTimeInMillis();
long differenceInMills = endCalendarTimeInMills - startCalendarTimeInMills;

//1秒 = 1000毫秒
long differenceInSecond = differenceInMills / 1000;
System.out.println("相差： " + differenceInSecond + "（秒）");

代碼執行結果：

相差： 90061（秒）

Process finished with exit code 0

2.3 ?分鍾

/*
 * 計算兩個日期之間的差值：
 *      日期1：2019-12-31 12:30:12
 *      日期2：2020-01-01 13:31:13
 */
Calendar startCalendar = Calendar.getInstance();
Calendar endCalendar = Calendar.getInstance();

// 手動設置時間
startCalendar.set(2019, Calendar.DECEMBER, 31, 12, 30, 12);
endCalendar.set(2020, Calendar.JANUARY, 1, 13, 31, 13);
startCalendar.set(Calendar.MILLISECOND, 0);
endCalendar.set(Calendar.MILLISECOND, 0);

// 計算毫秒差值
long startCalendarTimeInMills = startCalendar.getTimeInMillis();
long endCalendarTimeInMills = endCalendar.getTimeInMillis();
long differenceInMills = endCalendarTimeInMills - startCalendarTimeInMills;

// 1秒 = 1000毫秒
long differenceInSecond = differenceInMills / 1000;

// 1分鍾 = 60秒
long differenceInMinute = differenceInSecond / 60;
System.out.println("相差： " + differenceInMinute + "（分鍾）");

代碼執行結果：

相差： 1501（分鍾）

Process finished with exit code 0

2.4 ?小時

/*
 * 計算兩個日期之間的差值：
 *      日期1：2019-12-31 12:30:12
 *      日期2：2020-01-01 13:31:13
 */
Calendar startCalendar = Calendar.getInstance();
Calendar endCalendar = Calendar.getInstance();

// 手動設置時間
startCalendar.set(2019, Calendar.DECEMBER, 31, 12, 30, 12);
endCalendar.set(2020, Calendar.JANUARY, 1, 13, 31, 13);
startCalendar.set(Calendar.MILLISECOND, 0);
endCalendar.set(Calendar.MILLISECOND, 0);

// 計算毫秒差值
long startCalendarTimeInMills = startCalendar.getTimeInMillis();
long endCalendarTimeInMills = endCalendar.getTimeInMillis();
long differenceInMills = endCalendarTimeInMills - startCalendarTimeInMills;

// 1秒 = 1000毫秒
long differenceInSecond = differenceInMills / 1000;

// 1分鍾 = 60秒
long differenceInMinute = differenceInSecond / 60;

// 1小時 = 60分鍾 = 3600秒
long differenceInHour = differenceInSecond / 3600;
System.out.println("相差： " + differenceInHour + "（小時）");

代碼執行結果：

相差： 25（小時）

Process finished with exit code 0

2.5 ? 時?分?秒?毫秒

/*
 * 計算兩個日期之間的差值：
 *      日期1：2019-12-31 12:30:12
 *      日期2：2020-01-01 13:31:13
 */
Calendar startCalendar = Calendar.getInstance();
Calendar endCalendar = Calendar.getInstance();

// 手動設置時間
startCalendar.set(2019, Calendar.DECEMBER, 31, 12, 30, 12);
endCalendar.set(2020, Calendar.JANUARY, 1, 13, 31, 13);
startCalendar.set(Calendar.MILLISECOND, 0);
endCalendar.set(Calendar.MILLISECOND, 0);

// 計算毫秒差值
long startCalendarTimeInMills = startCalendar.getTimeInMillis();
long endCalendarTimeInMills = endCalendar.getTimeInMillis();
long differenceInMills = endCalendarTimeInMills - startCalendarTimeInMills;

// 1秒 = 1000毫秒
long differenceInSecond = differenceInMills / 1000;

// 1分鍾 = 60秒
long differenceInMinute = differenceInSecond / 60;

// 1小時 = 60分鍾 = 3600秒
long differenceInHour = differenceInSecond / 3600;

System.out.println("相差： " +
        (differenceInSecond / 3600) + "小時" +
        (differenceInSecond % 3600) / 60 + "分鍾" +
        (differenceInSecond % 3600 % 60) + "秒" +
        (differenceInMills % 1000) + "毫秒");

代碼執行結果：

相差： 25小時1分鍾1秒0毫秒

Process finished with exit code 0

三、時間比較

3.1 兩個日期相差幾天？

public static void main(String[] args) {

    /*
     * 計算兩個日期之間的差值：
     *      日期1：2019-12-31 12:30:12
     *      日期2：2020-01-01 13:31:13
     */
    Calendar calendar1 = Calendar.getInstance();
    Calendar calendar2 = Calendar.getInstance();

    calendar1.set(2019, Calendar.DECEMBER, 31, 12, 30, 12);
    calendar2.set(2020, Calendar.JANUARY, 1, 13, 31, 13);
    calendar1.set(Calendar.MILLISECOND, 0);
    calendar2.set(Calendar.MILLISECOND, 0);

    // 1.獲取日期毫秒數
    long timeInMills1 = calendar1.getTimeInMillis();
    long timeInMills2 = calendar2.getTimeInMillis();

    // 2.計算：本日期是自1900年以來的第幾天？
    long days1 = timeInMills1 / 1000 / 3600 / 24;
    long days2 = timeInMills2 / 1000 / 3600 / 24;
    System.out.println("日期 " + calendar1.getTime() + 
                       " 是1900年以來的第" + days1 + "天");
    System.out.println("日期 " + calendar2.getTime() + 
                       " 是1900年以來的第" + days2 + "天");

    // 3.計算日期相差的天數
    long differenceDays = days2 - days1;
    System.out.println("兩個日期相差：" + differenceDays + "天");
}

代碼執行結果：

日期 Tue Dec 31 12:30:12 CST 2019 是1900年以來的第18261天
日期 Wed Jan 01 13:31:13 CST 2020 是1900年以來的第18262天
兩個日期相差：1天

Process finished with exit code 0