Date帮助类

//得到两个日期之间相隔多少个月
	public static int getDifferMonth(Date date1, Date date2)
	{
		int difMonth = 
			(date2.getYear()-date1.getYear())*12+(date2.getMonth()-date1.getMonth());
		return Math.abs(difMonth); 
	}

package cn.com.eatlab.report.util;

import java.util.Calendar;
import java.util.Date;

public class DateUtils {

	/**
	 * 得到某个月的开始和结束日期 
	 * @param monthNum 0本月 -1，上个月，依次类推
	 * @return
	 */
	@SuppressWarnings("deprecation")
	public static Date[] getDateFirstDayAndLastDay(Integer monthNum){
			Calendar calendar1 = Calendar.getInstance();
				
				int month = calendar1.get(Calendar.MONTH);//当前月份 monthNum=-1，-2.。。2013-04-24 11:30:16
				System.out.println("当前月份：Calendar.MONTH："+month);
				calendar1.set(Calendar.MONTH, month+monthNum);//2013-02-24 11:30:16
				//得到月最后一天  天数
				calendar1.set(Calendar.MONTH, calendar1.get(Calendar.MONTH)+1);
				calendar1.set(Calendar.DATE,1);
				calendar1.add(Calendar.DATE, -1);//本月最后一天
				int lastDay = calendar1.get(Calendar.DATE);
				
				calendar1.set(Calendar.MONTH, month+monthNum);
				calendar1.set(Calendar.DATE, 1);
				calendar1.set(Calendar.HOUR_OF_DAY,0);
				calendar1.set(Calendar.MINUTE,0);
				calendar1.set(Calendar.SECOND,0);
				Date date1 = calendar1.getTime();
				
				calendar1.set(Calendar.DATE, lastDay);
				calendar1.set(Calendar.HOUR_OF_DAY,23);
				calendar1.set(Calendar.MINUTE,59);
				calendar1.set(Calendar.SECOND,59);
				Date date2 = calendar1.getTime();
		
				Date[] dates = new Date[2];	
				dates[0] = date1;
				dates[1] = date2;
				return dates;
	}
	/**
	 * 得到前preMonthNum个月的天数，0表示本月，-1 上一个月
	 * @param preMonthNum
	 * @return
	 */
	public static Integer getDayNumOfMonth(Integer preMonthNum){
		Calendar calendar1 = Calendar.getInstance();
		int month = calendar1.get(Calendar.MONTH);
		calendar1.set(Calendar.MONTH, month+preMonthNum);
		calendar1.set(Calendar.MONTH, calendar1.get(Calendar.MONTH)+1);
		calendar1.set(Calendar.DATE,1);
		calendar1.add(Calendar.DATE, -1);//本月最后一天
		int lastDay = calendar1.get(Calendar.DATE);
		return lastDay;
	}
public static String dateFormat(java.util.Date date) {
//		java.text.SimpleDateFormat sdf=new java.text.SimpleDateFormat("yyyy/MM/dd HH:mm:ss"); 
//        String c1=sdf.format(date);
        
//        System.out.println("完整时间格式："+date.toLocaleString());
        
        String tempTimeStr = "";
        
        //得到需要比较的时间的年月日
        int tempDate = date.getDate();
        int tempMonth = date.getMonth()+1;
        int tempYear = date.getYear()+1900;
       // System.out.println(tempDate+" "+tempMonth+" "+tempYear);
        
        //得到当前时间的年月日
          
        Calendar now = Calendar.getInstance();
      //  System.out.println("now:"+now.toString());
        //System.out.println("date:"+now.get(Calendar.DATE)+"-month:"+now.get(Calendar.MONTH)+"-year:"+now.get(Calendar.YEAR));
        int nowDate = now.get(Calendar.DATE);
        int nowMonth = now.get(Calendar.MONTH)+1;
        int nowYear = now.get(Calendar.YEAR);
        if(nowYear >tempYear ){//上年
        	java.text.SimpleDateFormat sdf=new java.text.SimpleDateFormat("yyyy/MM/dd"); 
        	tempTimeStr = sdf.format(date);
        }else if( nowMonth-tempMonth >=1 ){//今年上个月 会更久
        	java.text.SimpleDateFormat sdf=new java.text.SimpleDateFormat("yyyy/MM/dd"); 
        	tempTimeStr = sdf.format(date);
        }else if( nowDate -tempDate >= 2){//前天 或者本月
        	java.text.SimpleDateFormat sdf=new java.text.SimpleDateFormat("MM/dd"); 
        	tempTimeStr = sdf.format(date);
        }else if(nowDate -tempDate ==1){//昨天
        	java.text.SimpleDateFormat sdf=new java.text.SimpleDateFormat("HH:mm"); 
        	tempTimeStr = "昨天";
        }else{//今天
        	java.text.SimpleDateFormat sdf=new java.text.SimpleDateFormat("HH:mm"); 
        	tempTimeStr = sdf.format(date);
        }
        
        return tempTimeStr;
	}

}