获取某一天的前多少天多少月多少年的时间

    import java.util.Calendar;  
    public class TestGetLastMonth {  
            /** 
             * 获取指定月的前一月（年）或后一月（年） 
             * @param dateStr 
             * @param addYear 
             * @param addMonth 
             * @param addDate 
             * @return 输入的时期格式为yyyy-MM，输出的日期格式为yyyy-MM 
             * @throws Exception 
             */  
            public static String getLastMonth(String dateStr,int addYear, int addMonth, int addDate) throws Exception {  
                  try {  
                  java.text.SimpleDateFormat sdf = new java.text.SimpleDateFormat("yyyy-MM");  
                  java.util.Date sourceDate = sdf.parse(dateStr);  
                  Calendar cal = Calendar.getInstance();  
                  cal.setTime(sourceDate);  
                  cal.add(Calendar.YEAR,addYear);  
                  cal.add(Calendar.MONTH, addMonth);  
                  cal.add(Calendar.DATE, addDate);  
      
                  java.text.SimpleDateFormat returnSdf = new java.text.SimpleDateFormat("yyyy-MM");  
                  String dateTmp = returnSdf.format(cal.getTime());  
                  java.util.Date returnDate = returnSdf.parse(dateTmp);  
                  return dateTmp;  
                  } catch (Exception e) {  
                  e.printStackTrace();  
                  throw new Exception(e.getMessage());  
                  }  
                  }   
              
            /** 
             * 获取指定月的前一月（年）或后一月（年） 
             * @param dateStr 
             * @param addYear 
             * @param addMonth 
             * @param addDate 
             * @return 输入的时期格式为yyyy-MM-dd，输出的日期格式为yyyy-MM-dd 
             * @throws Exception 
             */  
            public static String getLastDay(String dateStr,int addYear, int addMonth, int addDate) throws Exception {  
                  try {  
                  java.text.SimpleDateFormat sdf = new java.text.SimpleDateFormat("yyyy-MM-dd");  
                  java.util.Date sourceDate = sdf.parse(dateStr);  
                  Calendar cal = Calendar.getInstance();  
                  cal.setTime(sourceDate);  
                  cal.add(Calendar.YEAR,addYear);  
                  cal.add(Calendar.MONTH, addMonth);  
                  cal.add(Calendar.DATE, addDate);  
      
                  java.text.SimpleDateFormat returnSdf = new java.text.SimpleDateFormat("yyyy-MM-dd");  
                  String dateTmp = returnSdf.format(cal.getTime());  
                  java.util.Date returnDate = returnSdf.parse(dateTmp);  
                  return dateTmp;  
                  } catch (Exception e) {  
                  e.printStackTrace();  
                  throw new Exception(e.getMessage());  
                  }  
                  }   
              
            /** 
             * 测试 
             * @param args 
             */  
            public static void main(String[] args) {  
                  try{  
                     System.out.println(TestGetLastMonth.getLastMonth("2011-06",0,-1,0));//2011-05  
                     System.out.println(TestGetLastMonth.getLastMonth("2011-06",0,-6,0));//2010-12  
                     System.out.println(TestGetLastMonth.getLastMonth("2011-06",-1,0,0));//2010-06  
                  }catch (Exception e) {  
                      
                }  
          
            }  
        }