java SimpleDateFormat和Calendar的转换

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

public class Demo {
	public static String Format(String str) throws ParseException {
		SimpleDateFormat sm = new SimpleDateFormat("yyyy-MM-dd");
		Date date = (Date) sm.parse(str);
		Calendar cl = Calendar.getInstance();
		cl.setTime(date);
		cl.add(Calendar.DATE, 1);
		return sm.format(cl.getTime());
	}

	public static int Format2(String str) throws ParseException {
		SimpleDateFormat sm = new SimpleDateFormat("yyyy-MM-dd");
		Date date = (Date) sm.parse(str);
		Calendar cl = Calendar.getInstance();
		cl.setTime(date);
		int a = cl.get(Calendar.DAY_OF_YEAR)-1 ;
		return a;
	}

	public static void main(String[] args) {
		try {
			Scanner sc = new Scanner(System.in);
			System.out.println("请输入日期(yyyy-MM-dd格式):");
			String str = sc.nextLine();
			System.out.println("该日期的后一天是：" + Format(str));
			System.out.println("该日期为该年的第几天：" + Format2(str));
		} catch (ParseException e) {
			System.out.println("无效数字！");
		}
	}
}