dateutil.java

Java写的一个学员系统

package cn.st.util;

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

public class DateUtil {
	private static DateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");

	public static Date createUpDate(String date) throws ParseException {

		formatter.format(formatter.parse(date));
		Calendar tempcl = formatter.getCalendar();

		int month = tempcl.get(Calendar.MONTH) + 1;
		int year = tempcl.get(Calendar.YEAR);
		int day = tempcl.get(Calendar.DAY_OF_MONTH);
		if (month == 1) {
			month = 12;
			year = year - 1;
		}else {
			month = month - 1;
		}
		if(month == 2) {
			day = (day > 28) ? 28 : day;
		}

		String date1 = year + "-" + month + "-" + day;

		return formatter.parse(date1);
	}

	public static Date createUpDateForCaiWu(String date) throws ParseException{
		formatter.format(formatter.parse(date));
		Calendar tempcl = formatter.getCalendar();

		int month = tempcl.get(Calendar.MONTH) + 1;
		int year = tempcl.get(Calendar.YEAR);
		int day = 0;
		if (month == 1) {
			month = 12;
			year = year - 1;
		} else {
			month = month - 1;
		}
		if(month == 1 || month == 3 || month == 5 || month == 7 || month == 8 ||
				month == 10 || month == 12) {
			day = 31;
		} else if(month == 2) {
			day = 28;
		} else {
			day = 30;
		}

		String date1 = year + "-" + month + "-" + day;

		return formatter.parse(date1);
	}

	/**
	 * 将一个Date输出成yyyy-mm-dd 字符串
	 * @author:zn
	 * @datetime:2007-3-23-上午10:46:52
	 * @param date
	 * @return
	 */
	public static String formatYYYYMMDD(Date date) {
		if(date != null) {
			return formatter.format(date);
		}

		return "";

	}

	/**
	 * 将一个yyyy-mm-dd解析成一个Date;如果输入的字符格式不对,则抛出异常.
	 * @author:zn
	 * @datetime:2007-3-23-上午10:47:39
	 * @param date
	 * @return Date
	 * @throws ParseException 如果输入的日期字符格式不对时抛出.
	 */
	public static Date parseYYYYMMDD(String date) throws ParseException {
		return formatter.parse(date);
	}

	public static void main(String [] args) {
		try {
			String str = formatter.format(createUpDate("2007-03-31"));
			System.out.println(str);
		} catch (ParseException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}