计算星期几的方法？

import javax.swing.JOptionPane;

public class DispalyWeek{

	public static void main(String[] args){

		String notice = "计算星期";

		String message = "请输入当天是星期几，如：周一就输入1";

		String message2 = "请输入天数，如：100";

		String whatDayString = JOptionPane.showInputDialog(null, message, notice, JOptionPane.QUESTION_MESSAGE);

		int whatDay = Integer.parseInt(whatDayString);

		whatDay = whatDay <= 7 ? (whatDay > 0 ? whatDay : 7) : 7;

		String numberOfDayString = JOptionPane.showInputDialog(null, message2, notice, JOptionPane.QUESTION_MESSAGE);

		int numberOfDay = Integer.parseInt(numberOfDayString);

		int newWhatDay;		

		if(numberOfDay <= 0){

			newWhatDay = whatDay;

		}else{

			int temp = (whatDay + numberOfDay % 7) % 7;

			newWhatDay = temp == 0 ? 7 : temp;

		}

		String output = "今天是星期" + whatDay +"', " + numberOfDay + "后是星期" + newWhatDay;

		JOptionPane.showMessageDialog(null, output);

	}

}