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第六章第二十四题(显示当前日期和时间)(Display current date and time) - 编程练习题答案

**6.24(显示当前日期和时间)程序清单2-7显示当前时间。改进这个例子,显示当前的日期和时间。程序清单6-12中日历例子可以提供一些如何求年、月和日的思路。

**6.24(Display current date and time) Listing 2.7, ShowCurrentTime.java, displays the current time. Revise this example to display the current date and time. The calendar example in Listing 6.12, PrintCalendar.java, should give you some ideas on how to find the year, month, and day.

下面是参考答案代码:

public class Ans6_24_page202 {
    /** Main method */
    public static void main(String[] args) {
        // Obtain the total milliseconds since midnight, Jan 1, 1970
        long totalMilliseconds = System.currentTimeMillis();

        // Obtain the total seconds since midnight, Jan 1, 1970
        long totalSeconds = totalMilliseconds / 1000;

        // Compute the current second in the minute in the hour
        long currentSecond = totalSeconds % 60;

        // Obtain the total minutes
        long totalMinutes = totalSeconds / 60;

        // Compute the current minute in the hour
        long currentMinute = totalMinutes % 60;

        // Obtain the total hours
        long totalHours = totalMinutes / 60;

        // Compute the current hour
        long currentHour = totalHours % 24;

        long totalDays = totalHours / 24;

        int currentYear = 1970;

        while (totalDays >= 365) {
            if (isLeapYear(currentYear))
                totalDays -= 366;
            else
                totalDays -= 365;
            currentYear++;
        }

        int currentMonths = 1;
        while (totalDays >= 28) {
            if (currentMonths == 1 || currentMonths == 3 || currentMonths == 5 || currentMonths == 7
                    || currentMonths == 8 || currentMonths == 10 || currentMonths == 12) {
                totalDays -= 31;
                currentMonths++;
            } else if (currentMonths == 4 || currentMonths == 6 || currentMonths == 9 || currentMonths == 11) {
                totalDays -= 30;
                currentMonths++;
            } else if (isLeapYear(currentYear) && currentMonths == 2) {
                totalDays -= 29;
                currentMonths++;
            } else {
                totalDays -= 28;
                currentMonths++;
            }
        }

        long currentDay;
        if (totalDays == 0)
            currentDay = 1;
        else
            currentDay = totalDays + 1;

        // GMT+8
        if (currentHour+8 >= 24) {
            currentHour = currentHour+8-24;
        }

        // Display results
        System.out.println("Current data is " + currentYear +
                "-"+currentMonths+"-"+currentDay+ "\nCurrent time is " +
                currentHour+":"+currentMinute+":"+currentSecond+" (GMT+8)");
    }

    /** Determine if it is a leap year */
    public static boolean isLeapYear(int year) {
        return year % 400 == 0 || (year % 4 == 0 && year % 100 != 0);
    }
}

适用Java语言程序设计与数据结构(基础篇)(原书第11版)Java语言程序设计(基础篇)(原书第10/11版)

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