编写一个方法days()，计算一个由年、月、日表示的日期是该年的第几天。在main()方法中提示用户输入日期的年、月、日，然后调用days()方法计算该日是该年的第几天，最后输出计算结果。-Write a method days (), calculate a year, month, date, said the first few days of the year. In the main () method prompts the user to enter dates in the year, month, day, and then call the days () method to calculate the day of the year the first few days, the final output results.