java 日期工具类(一)

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

/**
 * 时间处理工具类 

 * 
 * @author Davint
 * @since 5.0
 * @version 1.0
 */
public class TimerUtil {

	private SimpleDateFormat sp = new SimpleDateFormat("yyyy-MM-dd");
	private static TimerUtil cc = new TimerUtil();

	public static TimerUtil getInstance() {
		return cc;
	}

	public static void main(String[] args) {
		TimerUtil timer=TimerUtil.getInstance();
		System.out.println(timer.getDaysByDate(timer.getDate("2012-04-01", "yyyy-MM-dd")));
		
	}
	
	//根据日期得到当月天数
	public int getDaysByDate(Date date) {
		Calendar ca=Calendar.getInstance();
		ca.setTime(date);
		int year=ca.get(Calendar.YEAR);
		int month=ca.get(Calendar.MONDAY)+1;
		int day=0;
		if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0) {
			if (month==2) {
				day=29;
			}
		}else {
			if (month==2) {
				day=28;
			} 
		}
		
		if (month==4||month==6||month==9||month==11) {
			day=30;
		}
		
		if (month==1||month==3||month==5||month==7||month==8||month==10||month==12) {
			day=31;
		}
		return day;
	}
	

	/**
	 * 上周一的日期
	 * 将周一作为一周的第一天
	 */
	public Date getLastWeekFirstDay() {
		Calendar ca = Calendar.getInstance();
		if (ca.get(Calendar.DAY_OF_WEEK)-1==0) {
			ca.add(Calendar.DATE, -1 * 7*2);
			ca.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY);
			return ca.getTime();
		}
		ca.add(Calendar.DATE, -1 * 7);
		ca.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY);
		return ca.getTime();
	}

	// 本周一日期
	public Date getThisWeekFirstDay() {
		Calendar ca=Calendar.getInstance();
		if (ca.get(Calendar.DAY_OF_WEEK)-1==0) {
			ca.add(Calendar.DATE, -1);
			ca.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY);
			return ca.getTime();
		}
		ca.add(Calendar.DATE, 0);
		ca.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY);
		return ca.getTime();
	}
	
	//两个月前的第一天
	public Date getLast2MonFirstDay() {
		Calendar cal=Calendar.getInstance();
		Date now=new Date();
		cal.setTime(now);
		cal.add(Calendar.MONTH, -1);
		int year=cal.get(Calendar.YEAR);
		int month=cal.get(Calendar.MONTH);
		String resultTime=year+"-"+month+"-01";
		Date date =null;
		try {
			date=sp.parse(resultTime);
		} catch (ParseException e) {
			e.printStackTrace();
		}
		return date;
	}
	
	// 上个月第一天日期
	public Date getLastMonFirstDay() {
		Calendar cal=Calendar.getInstance();
		Date now=new Date();
		cal.setTime(now);
		int year=cal.get(Calendar.YEAR);
		int month=cal.get(Calendar.MONTH);
		String resultTime=year+"-"+month+"-01";
		Date date =null;
		try {
			date=sp.parse(resultTime);
		} catch (ParseException e) {
			e.printStackTrace();
		}
		return date;
	}

	// 本月第一天
	public Date getThisMonFirstDay() {
		Calendar cal = Calendar.getInstance();
		int year = cal.get(Calendar.YEAR);
		int month = cal.get(Calendar.MONTH) + 2;
		cal.set(Calendar.DAY_OF_MONTH, 1);
		cal.add(Calendar.DAY_OF_MONTH, -1);
		int day = cal.get(Calendar.DAY_OF_MONTH);
		String months = "";
		String days = "";
		if (month >





 1) {
			month--;
		} else {
			year--;
			month = 12;
		}
		if (!(String.valueOf(month).length() > 1)) {
			months = "0" + month;
		} else {
			months = String.valueOf(month);
		}
		if (!(String.valueOf(day).length() > 1)) {
			days = "0" + day;
		} e