java Calendar 计算时间

计算当前时间距与计算时间相差多久：

package num_1;

import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.Scanner;

public class test22 {
	public static void main(String[] args) throws ParseException {
		Scanner sc = new Scanner(System.in);
		System.out.println("退出请输入：exit");
		while (true) {
			System.out.print("请输入您要查询的时间(year-month-day)：");
			String str = sc.nextLine();
			if (str.equalsIgnoreCase("exit")) {
				System.exit(0);
				break;
			} else {
				DateFormat df = new SimpleDateFormat("yyyy-MM-dd");
				Date date = df.parse(str);
				Calendar cal = new GregorianCalendar();
				long now = cal.getInstance().getTimeInMillis();
				long before = date.getTime();
				if (now - before > 0) {
					long timeMillis = (now - before) / 1000 / 60 / 60 / 24;
					if (timeMillis > 365) {
						long year = timeMillis / 365;
						long month = timeMillis % 365 / 30;
						long day = timeMillis % 365 % 30;
						System.out.println("您输入的时间距今天" + timeMillis + "天");
						System.out.println("                               也就是 " + year + "年零" + month + "个月"
								+ day + "天");
					} else {
						System.out.println("您输入的时间距今天" + timeMillis + "天");
					}
				}
				if (now - before < 0) {
					long timeMillis = (before - now) / 1000 / 60 / 60 / 24;
					if (timeMillis > 365) {
						long year = timeMillis / 365;
						long month = timeMillis % 365 / 30;
						long day = timeMillis % 365 % 30;
						System.out.println("今天距您输入的时间" + timeMillis + "天");
						System.out.println("                               也就是 " + year + "年零" + month + "个月"
								+ day + "天");
					} else {
						System.out.println("今天距您输入的时间" + timeMillis + "天");
					}
				}

			}
		}

	}

}