Java编写的日历，输入年月，输出这个月的日期与星期
修改前的代码：
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Scanner;
public class calendar {
static int year, month, yearFirstDay, monthFirstDay; // 定义静态变量，以便其它类调用
public static boolean isLeapYear(int y) {// 判断是否是闰年
return ((y % 4 == 0 && y % 100 != 0) || (y % 400 == 0));
}
public static int getMonthDay(int m) {// 获取每个月的天数
switch (m) {
case 1:
case 3:
case 5:
case 7:
case 8:
case 10:
case 12:
return 31;
case 4:
case 6:
case 9:
case 11:
return 30;
case 2:
if (isLeapYear(year))// 判断是否是闰年
return 29;
else
return 28;
default:
return 0;
}
}
public static void getYearFirstDay() {// 计算该年第一天是星期几
long n = year * 365;
for (int i = 1; i < year; i++)
if (isLeapYear(i))// 判断是否是闰年
n += 1;
yearFirstDay = (int) n % 7;
}
public static void getMonthFirstDay() {// 计算该年第一天是星期几
getYearFirstDay();
int n = yearFirstDay;
for (int i = 1; i < month; i++)
n += getMonthDay(i);
monthFirstDay = n % 7;
}
public static void printTitleWeek() {// 打印表头
System.out.println("===========================");
System.out.println("日 一 二 三 四 五 六");
}
public static void printMonths() {// 逐月打印该年的日历
for (int m = 1; m <= 12; m++) // 循环月份
{
System.out.println(m + "月");
printTitleWeek();
for (int j = 1; j <= yearFirstDay; j++) {// 按每个月第一天是星期几打印相应的空格
System.out.print(" ");
}
int monthDay = getMonthDay(m); // 获取每个月的天数
for (int d = 1; d <= monthDay; d++) {
if (d < 10)// 以下4行对输出格式化
System.out.print(d + " ");
else
System.out.print(d + " ");
yearFirstDay = (yearFirstDay + 1) % 7; // 每打印一天后，反应第二天是星期几
if (yearFirstDay == 0) // 如果第二天是星期天，便换行。
System.out.println();
}
System.out.println('\n');
}
}
public static void printMonth() {// 只打印该月的日历
System.out.println(month + "月");
printTitleWeek();
for (int j = 1; j <= monthFirstDay; j++) {// 按每个月第一天是星期几打印相应的空格
System.out.print(" ");
}
int monthDay = getMonthDay(month); // 获取每个月的天数
for (int d = 1; d <= monthDay; d++) {
if (d < 10)// 以下4行对输出格式化
System.out.print(d + " ");
else
System.out.print(d + " ");
monthFirstDay = (monthFirstDay + 1) % 7; // 每打印一天后，反应第二天是星期几
if (monthFirstDay == 0) // 如果第二天是星期天，便换行。
System.out.println();
}
System.out.println('\n');
}
public static void main(String[] args) throws IOException {
InputStreamReader ir; // 以下接受从控制台输入
BufferedReader in;
ir = new InputStreamReader(System.in);
in = new BufferedReader(ir);
System.out.print("请输入年份：");
String y = in.readLine();
year = Integer.parseInt(y);
System.out.print("请输入月份：");
String m = in.readLine();
month = Integer.parseInt(m);
//getYearFirstDay(); // 计算该年第一天是星期几
getMonthFirstDay(); // 计算该月第一天是星期几
System.out.println("\n " + year + "年 ");
//printMonths();
printMonth();
}
}
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修改后的代码：
import java.util.Scanner;
public class calendar {
public static void main(String[] args) {
for (int g = 0; g < 100; g++) {
Scanner in = new Scanner(System.in);
System.out.println("\n请输入年份：");
int year = in.nextInt();
System.out.println("请输入月份：");
int month = in.nextInt();
int sum = 0;
int k = 0;
for (int i = 1; i <= month - 1; i++) {
if (i == 2) {
if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0) {
sum = sum + 29;
} else {
sum = sum + 28;
}
} else {
if (i == 4 || i == 6 || i == 9 || i == 11) {
sum = sum + 30;
} else {
sum = sum + 31;
}
}
}
for (int a = 1900; a <= year - 1; a++) {
if (a % 4 == 0 && a % 100 != 0 || a % 400 == 0) {
sum = sum + 366;
} else {
sum += 365;
}
}
sum += 1;
int wekday = sum % 7;
System.out.println("日\t一\t二\t三\t四\t五\t六");
for (int j = 1; j <= wekday; j++) {
System.out.print("\t");
}
if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0) {
if (month == 2) {
k = 29;
} else if (month == 4 || month == 6 || month == 9 || month == 11) {
k = 30;
} else {
k = 31;
}
} else {
if (month == 2) {
k = 28;
} else if (month == 4 || month == 6 || month == 9 || month == 11) {
k = 30;
} else {
k = 31;
}
}
for (int i = 1; i <= k; i++) {
if (sum % 7 == 6) {
System.out.print(i + "\n");
} else {
System.out.print(i + "\t");
}
sum++;
}
}
}
}
![关于calendar修改前的代码和修改后的代码-LMLPHP]( "关于calendar修改前的代码和修改后的代码-LMLPHP")