java 已知一个Date(),获取前一天和后一天

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

public class DateUtil {
    
    public static void main(String[] args) {
        Date date = new Date();
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        String specifiedDay = sdf.format(date);
        System.out.println(getSpecifiedDayBefore(specifiedDay));
        System.out.println(getSpecifiedDayAfter(specifiedDay));
    }
    
    /**
     * 获得指定日期的前一天
     * 
     * @param specifiedDay
     * @return
     * @throws Exception
     */
    public static String getSpecifiedDayBefore(String specifiedDay) {//可以用new Date().toLocalString()传递参数
        Calendar c = Calendar.getInstance();
        Date date = null;
        try {
            date = new SimpleDateFormat("yy-MM-dd").parse(specifiedDay);
        } catch (ParseException e) {
            e.printStackTrace();
        }
        c.setTime(date);
        int day = c.get(Calendar.DATE);
        c.set(Calendar.DATE, day - 1);

        String dayBefore = new SimpleDateFormat("yyyy-MM-dd").format(c
                .getTime());
        return dayBefore;
    }

    /**
     * 获得指定日期的后一天
     * 
     * @param specifiedDay
     * @return
     */
    public static String getSpecifiedDayAfter(String specifiedDay) {
        Calendar c = Calendar.getInstance();
        Date date = null;
        try {
            date = new SimpleDateFormat("yy-MM-dd").parse(specifiedDay);
        } catch (ParseException e) {
            e.printStackTrace();
        }
        c.setTime(date);
        int day = c.get(Calendar.DATE);
        c.set(Calendar.DATE, day + 1);

        String dayAfter = new SimpleDateFormat("yyyy-MM-dd")
                .format(c.getTime());
        return dayAfter;
    }
}