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

public class Main {


    public static void main(String[] args) throws ParseException {
        Date firstDay = getFirstDayOfWeek(2017,51);
        Date lastDay  = getLastDayOfWeek(2017,51);
        SimpleDateFormat  formatter = new SimpleDateFormat("yyyy-MM-dd");
        String dateString = formatter.format(firstDay);
        String dateString1 = formatter.format(lastDay);
        System.out.println(dateString);
        System.out.println(dateString1);
    }


    /**
     * 获取某周得第一天
     * @param year 年
     * @param week 周
     * @return
     */
    public static Date getFirstDayOfWeek(int year, int week){
        Calendar c = new GregorianCalendar();

        c.set(Calendar.YEAR, year);
        c.set(Calendar.WEEK_OF_YEAR,  week);
        c.setFirstDayOfWeek(Calendar.MONDAY);
        c.set(Calendar.DAY_OF_WEEK, c.getFirstDayOfWeek());
        c.set(Calendar.HOUR, 0);
        c.set(Calendar.MINUTE, 0);
        c.set(Calendar.SECOND, 0);

        return c.getTime();
    }

    /**
     * 获取某周得最后一天
     * @param year 年
     * @param week 周
     * @return
     */
    public static Date getLastDayOfWeek(int year, int week){
        Calendar c = new GregorianCalendar();

        c.set(Calendar.YEAR, year);
        c.set(Calendar.WEEK_OF_YEAR,  week);
        c.setFirstDayOfWeek(Calendar.MONDAY);
        c.set(Calendar.DAY_OF_WEEK, c.getFirstDayOfWeek() + 5);
        c.set(Calendar.HOUR, 23);
        c.set(Calendar.MINUTE, 59);
        c.set(Calendar.SECOND, 59);

        return c.getTime();
    }

}