求某个日期的前几天

    /**
     * 转String的日期类型到java.sql.date(月初前6天按照上月月末算)
     * @param String:要转换的String型日期
     * @return java.sql.Date :返回转换过的类型
     * @throws
     */
    public static java.sql.Date toSqlDate2(String date) {
     String result="";
     
     String a=date.substring(8,10);
  int b=Integer.parseInt(a);
  
  if (b<6)
  {
   result=date.substring(0,4)+"-"+date.substring(5,7)+"-01";
   SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");
   String str=result;
   Date dt=sdf.parse(str,new ParsePosition(0));
   Calendar rightNow = Calendar.getInstance();
   rightNow.setTime(dt);
   rightNow.add(Calendar.DATE,-1);//你要加减的日期
   Date dt1=rightNow.getTime();
   date=sdf.format(dt1);
  }
  
        java.sql.Date d = null;
        try {
          if (date != null && !date.equals("")) {
            //date=date.substring(0,4)+"-"+date.substring(4,6)+"-"+date.substring(6);
            d = java.sql.Date.valueOf(date);
          }
        }
        catch (IllegalArgumentException ex) {
          d = null;
        }
        return d;
      }  
     

另一个单独主程序

public class test {

 public static void main(String[] args) {
  // TODO Auto-generated method stub
  //String date=Utility.TIMER_START_DATE;
  //int month = Integer.parseInt(date.substring(5,7))-1;
  Date a =Utility.toSqlDate2("2006-09-05");
  System.out.println(a);

 }

}