java中IO练习：从键盘上输入任意年份和月份，输出该月份的日历，并输出到文件中。

好的，这是一个比较复杂的问题，我来分步骤回答。

首先，我们需要从键盘上读取用户输入的年份和月份。可以使用 `Scanner` 类来实现：

Scanner scanner = new Scanner(System.in);
System.out.println("请输入年份：");
int year = scanner.nextInt();
System.out.println("请输入月份：");
int month = scanner.nextInt();

接着，我们需要计算出该月份的日历。我们可以使用 `Calendar` 类来实现：

Calendar calendar = Calendar.getInstance();
calendar.set(year, month - 1, 1); // 将日历设置为该年该月的第一天
int maxDay = calendar.getActualMaximum(Calendar.DAY_OF_MONTH); // 获取该月份的最大天数
int firstDayOfWeek = calendar.get(Calendar.DAY_OF_WEEK); // 获取该月份第一天是星期几

// 输出日历
System.out.printf("%d年%d月\n", year, month);
System.out.println("日\t一\t二\t三\t四\t五\t六");
for (int i = 1; i < firstDayOfWeek; i++) {
    System.out.print("\t");
}
for (int i = 1; i <= maxDay; i++) {
    System.out.print(i + "\t");
    if ((firstDayOfWeek + i - 1) % 7 == 0) {
        System.out.println();
    }
}

最后，我们需要将日历输出到文件中。可以使用 `PrintWriter` 类来实现：

PrintWriter writer = new PrintWriter(new FileOutputStream("calendar.txt"));
writer.printf("%d年%d月\n", year, month);
writer.println("日\t一\t二\t三\t四\t五\t六");
for (int i = 1; i < firstDayOfWeek; i++) {
    writer.print("\t");
}
for (int i = 1; i <= maxDay; i++) {
    writer.print(i + "\t");
    if ((firstDayOfWeek + i - 1) % 7 == 0) {
        writer.println();
    }
}
writer.close();

完整代码如下：

import java.io.FileOutputStream;
import java.io.PrintWriter;
import java.util.Calendar;
import java.util.Scanner;

public class CalendarDemo {
    public static void main(String[] args) throws Exception {
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入年份：");
        int year = scanner.nextInt();
        System.out.println("请输入月份：");
        int month = scanner.nextInt();

        Calendar calendar = Calendar.getInstance();
        calendar.set(year, month - 1, 1);
        int maxDay = calendar.getActualMaximum(Calendar.DAY_OF_MONTH);
        int firstDayOfWeek = calendar.get(Calendar.DAY_OF_WEEK);

        System.out.printf("%d年%d月\n", year, month);
        System.out.println("日\t一\t二\t三\t四\t五\t六");
        for (int i = 1; i < firstDayOfWeek; i++) {
            System.out.print("\t");
        }
        for (int i = 1; i <= maxDay; i++) {
            System.out.print(i + "\t");
            if ((firstDayOfWeek + i - 1) % 7 == 0) {
                System.out.println();
            }
        }

        PrintWriter writer = new PrintWriter(new FileOutputStream("calendar.txt"));
        writer.printf("%d年%d月\n", year, month);
        writer.println("日\t一\t二\t三\t四\t五\t六");
        for (int i = 1; i < firstDayOfWeek; i++) {
            writer.print("\t");
        }
        for (int i = 1; i <= maxDay; i++) {
            writer.print(i + "\t");
            if ((firstDayOfWeek + i - 1) % 7 == 0) {
                writer.println();
            }
        }
        writer.close();
    }
}

希望能够帮到你！