获取参数日期的上月月末日期及下月月初日期

    public static String getNewDate(String strDate,Integer flag){ 
       if(null==strDate || "".equals(strDate) || null==flag ){
    	   return null ;
       }
       Calendar cal = Calendar.getInstance(); 
       String[] dateArr = strDate.split("-");
       int year = Integer.parseInt(dateArr[0]);
       int month = Integer.parseInt(dateArr[1]);
       cal.set(Calendar.YEAR, year);
       if(flag.intValue()==1){
    	   cal.set(Calendar.MONTH, month);
    	   cal.set(Calendar.DATE,1);
       }
       if(flag.intValue()==-1){
    	   cal.set(Calendar.MONTH, month-2);
    	   cal.set(Calendar.DATE, cal.getActualMaximum(Calendar.DATE)); 
       }   
       return new SimpleDateFormat("yyyy-MM-dd").format(cal.getTime());        
    }