Calculate time using calendar

Use Calendar computing time

One . Type conversion

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();
}

Two . Time calculation

2.1 ? millisecond

/* *  Calculate the difference between two dates ： *  date 1：2019-12-31 12:30:12 *  date 2：2020-01-01 13:31:13 */
Calendar startCalendar = Calendar.getInstance();
Calendar endCalendar = Calendar.getInstance();

//  Set the time manually 
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(" Difference between ：" + differenceInMills + "（ millisecond ）");

Code execution result ：

Difference between ： 90061000（ millisecond ）

Process finished with exit code 0

2.2 ? second

/* *  Calculate the difference between two dates ： *  date 1：2019-12-31 12:30:12 *  date 2：2020-01-01 13:31:13 */
Calendar startCalendar = Calendar.getInstance();
Calendar endCalendar = Calendar.getInstance();

//  Set the time manually 
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 second  = 1000 millisecond 
long differenceInSecond = differenceInMills / 1000;
System.out.println(" Difference between ： " + differenceInSecond + "（ second ）");

Code execution result ：

Difference between ： 90061（ second ）

Process finished with exit code 0

2.3 ? minute

/* *  Calculate the difference between two dates ： *  date 1：2019-12-31 12:30:12 *  date 2：2020-01-01 13:31:13 */
Calendar startCalendar = Calendar.getInstance();
Calendar endCalendar = Calendar.getInstance();

//  Set the time manually 
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);

//  Calculate the millisecond difference 
long startCalendarTimeInMills = startCalendar.getTimeInMillis();
long endCalendarTimeInMills = endCalendar.getTimeInMillis();
long differenceInMills = endCalendarTimeInMills - startCalendarTimeInMills;

// 1 second  = 1000 millisecond 
long differenceInSecond = differenceInMills / 1000;

// 1 minute  = 60 second 
long differenceInMinute = differenceInSecond / 60;
System.out.println(" Difference between ： " + differenceInMinute + "（ minute ）");

Code execution result ：

Difference between ： 1501（ minute ）

Process finished with exit code 0

2.4 ? Hours

/* *  Calculate the difference between two dates ： *  date 1：2019-12-31 12:30:12 *  date 2：2020-01-01 13:31:13 */
Calendar startCalendar = Calendar.getInstance();
Calendar endCalendar = Calendar.getInstance();

//  Set the time manually 
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);

//  Calculate the millisecond difference 
long startCalendarTimeInMills = startCalendar.getTimeInMillis();
long endCalendarTimeInMills = endCalendar.getTimeInMillis();
long differenceInMills = endCalendarTimeInMills - startCalendarTimeInMills;

// 1 second  = 1000 millisecond 
long differenceInSecond = differenceInMills / 1000;

// 1 minute  = 60 second 
long differenceInMinute = differenceInSecond / 60;

// 1 Hours  = 60 minute  = 3600 second 
long differenceInHour = differenceInSecond / 3600;
System.out.println(" Difference between ： " + differenceInHour + "（ Hours ）");

Code execution result ：

Difference between ： 25（ Hours ）

Process finished with exit code 0

2.5 ? when ? branch ? second ? millisecond

/* *  Calculate the difference between two dates ： *  date 1：2019-12-31 12:30:12 *  date 2：2020-01-01 13:31:13 */
Calendar startCalendar = Calendar.getInstance();
Calendar endCalendar = Calendar.getInstance();

//  Set the time manually 
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);

//  Calculate the millisecond difference 
long startCalendarTimeInMills = startCalendar.getTimeInMillis();
long endCalendarTimeInMills = endCalendar.getTimeInMillis();
long differenceInMills = endCalendarTimeInMills - startCalendarTimeInMills;

// 1 second  = 1000 millisecond 
long differenceInSecond = differenceInMills / 1000;

// 1 minute  = 60 second 
long differenceInMinute = differenceInSecond / 60;

// 1 Hours  = 60 minute  = 3600 second 
long differenceInHour = differenceInSecond / 3600;

System.out.println(" Difference between ： " +
        (differenceInSecond / 3600) + " Hours " +
        (differenceInSecond % 3600) / 60 + " minute " +
        (differenceInSecond % 3600 % 60) + " second " +
        (differenceInMills % 1000) + " millisecond ");

Code execution result ：

Difference between ： 25 Hours 1 minute 1 second 0 millisecond

Process finished with exit code 0

3、 ... and 、 Time comparison

3.1 The two dates differ by a few days ？

public static void main(String[] args) {
    

    /* *  Calculate the difference between two dates ： *  date 1：2019-12-31 12:30:12 *  date 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. Get date milliseconds 
    long timeInMills1 = calendar1.getTimeInMillis();
    long timeInMills2 = calendar2.getTimeInMillis();

    // 2. Calculation ： This date is from 1900 A few days since ？
    long days1 = timeInMills1 / 1000 / 3600 / 24;
    long days2 = timeInMills2 / 1000 / 3600 / 24;
    System.out.println(" date  " + calendar1.getTime() + 
                       "  yes 1900 For the first time since " + days1 + " God ");
    System.out.println(" date  " + calendar2.getTime() + 
                       "  yes 1900 For the first time since " + days2 + " God ");

    // 3. Calculate the number of days between dates 
    long differenceDays = days2 - days1;
    System.out.println(" Difference between two dates ：" + differenceDays + " God ");
}

Code execution result ：

date Tue Dec 31 12:30:12 CST 2019 yes 1900 For the first time since 18261 God
date Wed Jan 01 13:31:13 CST 2020 yes 1900 For the first time since 18262 God
Difference between two dates ：1 God

Process finished with exit code 0