如何在终端上正确打印月历
How to Properly print Month Calendar on Terminal
您好，在此先感谢您的帮助。我有一个程序应该根据用户输入的月份和年份打印当前月份的日历。该程序大部分工作，但我遇到格式问题，并且该月的第一天未在正确的日期开始。
示例输出：
October 2020
------------------------------
Sun Mon Tue Wed Thu Fri Sat
1 2 3 4 5
6 7 8 9 10 11 12
13 14 15 16 17 18 19
20 21 22 23 24 25 26
27 28 29 30 31
2020 年 10 月将从星期四开始，但 1 印在 Mon 下。 10 月 4 日是星期日，因此新行应该从星期日开始。
请参阅附件中的代码。再次感谢
import java.util.*;
public class CalendarMonthDisplay {
public static void main(String[] args) {
Scanner input = new Scanner(System.in); //Scan for user input
System.out.print("Please enter a month between 1 and 12 (e.g. 5): "); //Prompt user to enter month
int m = input.nextInt();
System.out.print("Please enter a full year (e.g. 2018): "); //Prompt user to enter year
int y = input.nextInt();
//Print calendar for the month of the year
if ( m < 1 || m > 12)
System.out.print("Wrong input! Please try again.");
else
printMonthCalendar(m, y);
}
static void printMonthCalendar (int m, int y) { //Display calendar in format above
int startDay = getStartDay(m, y);
int numDaysInMonths = getNumDaysInMonth(m, y);
printMonthHeader(m, y);
printMonthBody(startDay, numDaysInMonths);
}
static void printMonthBody (int startDay, int numDaysInMonths) { //Display the days in the calendar
int i;
for (i = 0; i <= startDay; i++)
System.out.print(" ");
for (i = 1; i <= numDaysInMonths; i++) {
if ( i < 10 )
System.out.print(" " + i );
else
System.out.print(" " + i + " ");
if ((startDay + i) % 7 == 0)
System.out.println();
}
System.out.println();
}
static void printMonthHeader (int m, int y) { //Display the header information
System.out.println("\t" + getMonthName(m) + " " + y);
System.out.println("------------------------------");
System.out.println(" Sun Mon Tue Wed Thu Fri Sat");
}
static String getMonthName (int m) {
String monthName = null;
switch (m) {
case 1: monthName = "January";
break;
case 2: monthName = "February";
break;
case 3: monthName = "March";
break;
case 4: monthName = "April";
break;
case 5: monthName = "May";
break;
case 6: monthName = "June";
break;
case 7: monthName = "July";
break;
case 8: monthName = "August";
break;
case 9: monthName = "September";
break;
case 10: monthName = "October";
break;
case 11: monthName = "November";
break;
case 12: monthName = "December";
}
return monthName;
}
static int getNumDaysInMonth (int m, int y) {
int numDaysInMonths= 0;
switch (m) {
case 1: case 3: case 5: case 7: case 8: case 10: case 12:
numDaysInMonths= 31;
break;
case 4: case 6: case 9: case 11:
numDaysInMonths = 30;
break;
case 2:
if (isLeapYear(y))
numDaysInMonths = 29;
else
numDaysInMonths = 28;
break;
}
return numDaysInMonths;
}
static boolean isLeapYear (int y) {
return (y % 400 == 0) || (y % 4 == 0 && y % 100 != 0);
// return true;
// return false;
}
static int getStartDay (int m, int y) {
// Adjust month number & year to fit Zeller's numbering system
if (m < 3)
m = m + 12;
y = y - 1;
int d = 1; //Set day parameter to 1
int k = y % 100; // Calculate year within century
int j = y / 100; // Calculate century term
int h = 0; // Day number of first day in month 'm'
h = ( d + ( 13 * ( m + 1 ) / 5 ) + k + ( k / 4 ) + ( j / 4 ) + ( 5 * j ) ) % 7;
// Convert Zeller's value to ISO value (1 = Mon, ... , 7 = Sun )
int dayNum = ( ( h + 5 ) % 7 ) + 1;
return dayNum;
}
}
我建议您使用 modern date-time API. Learn more about the modern date-time API from Trail: Date Time。
import java.time.LocalDate;
import java.time.YearMonth;
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner input = new Scanner(System.in); // Scan for user input
System.out.print("Please enter a month between 1 and 12 (e.g. 5): "); // Prompt user to enter month
int m = input.nextInt();
System.out.print("Please enter a full year (e.g. 2018): "); // Prompt user to enter year
int y = input.nextInt();
printMonth(y, m);
}
static void printMonth(int year, int month) {
YearMonth ym = YearMonth.of(year, month);
System.out.println("Sun Mon Tue Wed Thu Fri Sat");
int counter = 1;
// Get day of week of 1st date of the month and print space for as many days as
// distant from SUN
int dayValue = LocalDate.of(year, month, 1).getDayOfWeek().getValue();
for (int i = 0; i < dayValue; i++, counter++) {
System.out.printf("%-4s", "");
}
for (int i = 1; i <= ym.getMonth().length(ym.isLeapYear()); i++, counter++) {
System.out.printf("%-4d", i);
// Break the line if the value of the counter is multiple of 7
if (counter % 7 == 0) {
System.out.println();
}
}
}
}
样本运行:
Please enter a month between 1 and 12 (e.g. 5): 9
Please enter a full year (e.g. 2018): 2020
Sun Mon Tue Wed Thu Fri Sat
1 2 3 4 5
6 7 8 9 10 11 12
13 14 15 16 17 18 19
20 21 22 23 24 25 26
27 28 29 30
注意：在 Formatter 了解格式化打印。
我不认为你的 getStartDay 方法 returns 是你期望的星期几。它似乎从星期三返回 1 到星期二返回 7。示例：
Month Start day of week getStartDay()
------------------------------------------------
July 2020 Wednesday 1
August 2020 Saturday 4
September 2020 Tuesday 7
October 2020 Thursday 2
您的代码中可能还有一两个问题，但我认为您应该首先解决这个基本问题。
这是一个很好的练习，你一定会学到的。对于生产代码，永远不会实现 Zeller 算法或任何其他算法来查找月份和星期几的长度。如 Arvind Kumar Avinash 的回答所示，标准库可以更可靠地完成此操作。
您好，在此先感谢您的帮助。我有一个程序应该根据用户输入的月份和年份打印当前月份的日历。该程序大部分工作，但我遇到格式问题，并且该月的第一天未在正确的日期开始。
示例输出：
October 2020
------------------------------
Sun Mon Tue Wed Thu Fri Sat
1 2 3 4 5
6 7 8 9 10 11 12
13 14 15 16 17 18 19
20 21 22 23 24 25 26
27 28 29 30 31
2020 年 10 月将从星期四开始，但 1 印在 Mon 下。 10 月 4 日是星期日，因此新行应该从星期日开始。
请参阅附件中的代码。再次感谢
import java.util.*;
public class CalendarMonthDisplay {
public static void main(String[] args) {
Scanner input = new Scanner(System.in); //Scan for user input
System.out.print("Please enter a month between 1 and 12 (e.g. 5): "); //Prompt user to enter month
int m = input.nextInt();
System.out.print("Please enter a full year (e.g. 2018): "); //Prompt user to enter year
int y = input.nextInt();
//Print calendar for the month of the year
if ( m < 1 || m > 12)
System.out.print("Wrong input! Please try again.");
else
printMonthCalendar(m, y);
}
static void printMonthCalendar (int m, int y) { //Display calendar in format above
int startDay = getStartDay(m, y);
int numDaysInMonths = getNumDaysInMonth(m, y);
printMonthHeader(m, y);
printMonthBody(startDay, numDaysInMonths);
}
static void printMonthBody (int startDay, int numDaysInMonths) { //Display the days in the calendar
int i;
for (i = 0; i <= startDay; i++)
System.out.print(" ");
for (i = 1; i <= numDaysInMonths; i++) {
if ( i < 10 )
System.out.print(" " + i );
else
System.out.print(" " + i + " ");
if ((startDay + i) % 7 == 0)
System.out.println();
}
System.out.println();
}
static void printMonthHeader (int m, int y) { //Display the header information
System.out.println("\t" + getMonthName(m) + " " + y);
System.out.println("------------------------------");
System.out.println(" Sun Mon Tue Wed Thu Fri Sat");
}
static String getMonthName (int m) {
String monthName = null;
switch (m) {
case 1: monthName = "January";
break;
case 2: monthName = "February";
break;
case 3: monthName = "March";
break;
case 4: monthName = "April";
break;
case 5: monthName = "May";
break;
case 6: monthName = "June";
break;
case 7: monthName = "July";
break;
case 8: monthName = "August";
break;
case 9: monthName = "September";
break;
case 10: monthName = "October";
break;
case 11: monthName = "November";
break;
case 12: monthName = "December";
}
return monthName;
}
static int getNumDaysInMonth (int m, int y) {
int numDaysInMonths= 0;
switch (m) {
case 1: case 3: case 5: case 7: case 8: case 10: case 12:
numDaysInMonths= 31;
break;
case 4: case 6: case 9: case 11:
numDaysInMonths = 30;
break;
case 2:
if (isLeapYear(y))
numDaysInMonths = 29;
else
numDaysInMonths = 28;
break;
}
return numDaysInMonths;
}
static boolean isLeapYear (int y) {
return (y % 400 == 0) || (y % 4 == 0 && y % 100 != 0);
// return true;
// return false;
}
static int getStartDay (int m, int y) {
// Adjust month number & year to fit Zeller's numbering system
if (m < 3)
m = m + 12;
y = y - 1;
int d = 1; //Set day parameter to 1
int k = y % 100; // Calculate year within century
int j = y / 100; // Calculate century term
int h = 0; // Day number of first day in month 'm'
h = ( d + ( 13 * ( m + 1 ) / 5 ) + k + ( k / 4 ) + ( j / 4 ) + ( 5 * j ) ) % 7;
// Convert Zeller's value to ISO value (1 = Mon, ... , 7 = Sun )
int dayNum = ( ( h + 5 ) % 7 ) + 1;
return dayNum;
}
}
我建议您使用 modern date-time API. Learn more about the modern date-time API from Trail: Date Time。
import java.time.LocalDate;
import java.time.YearMonth;
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner input = new Scanner(System.in); // Scan for user input
System.out.print("Please enter a month between 1 and 12 (e.g. 5): "); // Prompt user to enter month
int m = input.nextInt();
System.out.print("Please enter a full year (e.g. 2018): "); // Prompt user to enter year
int y = input.nextInt();
printMonth(y, m);
}
static void printMonth(int year, int month) {
YearMonth ym = YearMonth.of(year, month);
System.out.println("Sun Mon Tue Wed Thu Fri Sat");
int counter = 1;
// Get day of week of 1st date of the month and print space for as many days as
// distant from SUN
int dayValue = LocalDate.of(year, month, 1).getDayOfWeek().getValue();
for (int i = 0; i < dayValue; i++, counter++) {
System.out.printf("%-4s", "");
}
for (int i = 1; i <= ym.getMonth().length(ym.isLeapYear()); i++, counter++) {
System.out.printf("%-4d", i);
// Break the line if the value of the counter is multiple of 7
if (counter % 7 == 0) {
System.out.println();
}
}
}
}
样本运行:
Please enter a month between 1 and 12 (e.g. 5): 9
Please enter a full year (e.g. 2018): 2020
Sun Mon Tue Wed Thu Fri Sat
1 2 3 4 5
6 7 8 9 10 11 12
13 14 15 16 17 18 19
20 21 22 23 24 25 26
27 28 29 30
注意：在 Formatter 了解格式化打印。
我不认为你的 getStartDay 方法 returns 是你期望的星期几。它似乎从星期三返回 1 到星期二返回 7。示例：
Month Start day of week getStartDay()
------------------------------------------------
July 2020 Wednesday 1
August 2020 Saturday 4
September 2020 Tuesday 7
October 2020 Thursday 2
您的代码中可能还有一两个问题，但我认为您应该首先解决这个基本问题。
这是一个很好的练习，你一定会学到的。对于生产代码，永远不会实现 Zeller 算法或任何其他算法来查找月份和星期几的长度。如 Arvind Kumar Avinash 的回答所示，标准库可以更可靠地完成此操作。