日期类

package com.jason.utils;

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.HashMap;
import java.util.Map;

public class DateUtil {
	/**
	 * 获取本月第一天和最后一天日期
	 * @return MAP{beginTime:本月的第一天}{endTime:本月的最后一天}
	 */
	public static Map<String, String> findThisMonth(){
		  Calendar cal = Calendar.getInstance();   
		  SimpleDateFormat datef=new SimpleDateFormat("yyyy-MM-dd");  
		  //获取本月的第一天            
	      cal.set(GregorianCalendar.DAY_OF_MONTH, 1);   
	      Date beginTime1=cal.getTime();  
	      String beginTime=datef.format(beginTime1);
		  //获取本月的最后一天     
	      cal.set( Calendar.DATE, 1 );  
	      cal.roll(Calendar.DATE, - 1 );  
	      Date endTime1=cal.getTime();  
	      String endTime=datef.format(endTime1);
	      
	      Map<String, String> map = new HashMap<String, String>();
		  map.put("beginTime", beginTime);
		  map.put("endTime", endTime);
		  return map;
	}
	/**
	  * 获取上个月的第一天和最后一天带时间
	  * 
	  * @return MAP{prevMonthFD:当前日期上个月的第一天}{prevMonthPD:当前日期上个月的最后一天}
	  */
	@SuppressWarnings("static-access")
	public static Map<String, String> findLastMonth() {
		  SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
	
		  Calendar cal = Calendar.getInstance();
		  GregorianCalendar gcLast = (GregorianCalendar) Calendar.getInstance();
		  Calendar calendar = Calendar.getInstance();
		  calendar.setTime(new Date());
	
		  calendar.add(Calendar.MONTH, -1);
		  Date theDate = calendar.getTime();
		  gcLast.setTime(theDate);
		  gcLast.set(Calendar.DAY_OF_MONTH, 1);
		  String day_first_prevM = df.format(gcLast.getTime());
		  //带时间
//		  StringBuffer str = new StringBuffer().append(day_first_prevM).append(
//		    " 00:00:00");
//		  day_first_prevM = str.toString();
		  
		  calendar.add(cal.MONTH, 1);
		  calendar.set(cal.DATE, 1);
		  calendar.add(cal.DATE, -1);
		  String day_end_prevM = df.format(calendar.getTime());
		  //带时间
//		  StringBuffer endStr = new StringBuffer().append(day_end_prevM).append(
//		    " 23:59:59");
//		  day_end_prevM = endStr.toString();
		  
		  Map<String, String> map = new HashMap<String, String>();
		  map.put("prevMonthFD", day_first_prevM);
		  map.put("prevMonthPD", day_end_prevM);
		  return map;
	 }
	/**
	 * 获取三个月前的日期和当天日期
	 * @return MAP{nowDate:当前日期}{threeMonthsAgoDate:3个月前的 日期}
	 */
	public static Map<String, String> findThreeMonthsAgo() {
		 // 取当前日期   
		 Date date = new Date();   
		 // 实例化日历类    
		 Calendar cal = Calendar.getInstance();   
		 // 设置日期   
		 cal.setTime(date);   
		 // 取3个月前的 日期   
		 cal.add(Calendar.MONTH,-3);
		 Date threeMonthAgoDate1 = cal.getTime();   
		   
		 // 以下是Date类型转换String类型  
		 SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");  
		 String nowDate=dateFormat.format(date);  
		 String threeMonthsAgoDate = dateFormat.format(threeMonthAgoDate1);
		 
		 Map<String, String> map = new HashMap<String, String>();
		 map.put("nowDate", nowDate);
		 map.put("threeMonthsAgoDate", threeMonthsAgoDate);
		 return map;
	}
	
	public static void main(String[] args) {
		Map<String, String> map =findThisMonth();
		System.out.println("本月第一天日期：" + map.get("beginTime"));
		System.out.println("本月最后一天日期：" + map.get("endTime"));
		
		Map<String, String> map1=findLastMonth();
		System.out.println("上月第一天日期：" + map1.get("prevMonthFD"));
		System.out.println("上月最后一天日期：" + map1.get("prevMonthPD"));
		
		Map<String, String> map2=findThreeMonthsAgo();
		System.out.println("当天日期：" + map2.get("nowDate"));
		System.out.println("三个月前日期：" + map2.get("threeMonthsAgoDate"));
	}
}