java 实现获取当天，当周，当月，当季，当年的时间段

由于项目需求，现在要做一个排行榜，需要按照时间（日，周，月，季，年）来从sql中查询数据。

1、首先要做的就是怎样判断当前的时间段

查询资料知：

项目中关于时间的使用：

1、获取时间 Date date=new Date(); date.getDate(); // System.currentTimeMills(); 都是返回long型的数据，

2、以某种格式输出

（1）SimpleDateFormat sdf=new SimpleDateFormat("yyyy--MM--dd HH:mm:ss " ); sdf.format(date)将date型转换成 String

（2）将String转换成Date型 ： sdf.parse(str); 将String类型解析成Date类型

3、对时间进行处理

Calendar 类 可以获取年月日

参看 http://www.apihome.cn/api/java/Calendar.html Calendar的使用文档

        /**
         * 获取当前日期与周一相差的天数
         * @return
         */
        public static int getMondayPlus(){
                Calendar day=Calendar.getInstance();
                int dayOfWeek=day.get(Calendar.DAY_OF_WEEK);
                if(dayOfWeek==1){ //一周中第一天（周日）
                        return -6;
                }else{
                        return 2-dayOfWeek;
                }
        }
        /**
         * 获得当天的起始时间
         * @return
         */
        public static Calendar getStartDate(Calendar today){
                today.set(Calendar.HOUR_OF_DAY,0);
                today.set(Calendar.MINUTE, 0);  
                today.set(Calendar.SECOND, 0);  
                today.set(Calendar.MILLISECOND, 0);  
                return today;
        }
        /**
         * 获取当天截止时间
         * @return
         */
        public static Calendar getEndDate(Calendar endToday){
                endToday.set(Calendar.HOUR_OF_DAY, 23);  
                endToday.set(Calendar.MINUTE, 59);  
                endToday.set(Calendar.SECOND, 59);  
                endToday.set(Calendar.MILLISECOND, 59);  
                return endToday;
        }
        /**
         * 获得当月起始时间
         * @return
         */
        public static Calendar getStartMounth(Calendar today){
                Calendar calendar = getStartDate(today);   
        calendar.set(Calendar.DAY_OF_MONTH, calendar.getActualMinimum(Calendar.DAY_OF_MONTH)); 
        return calendar;
        }
        /**
         * 获得当月结束时间
         * @return
         */
        public static Calendar getEndMounth(Calendar endToday){
                Calendar endMounth=getEndDate(endToday);
                endMounth.set(Calendar.DAY_OF_MONTH, endMounth.getActualMaximum(endMounth.DAY_OF_MONTH));
                return endMounth;
        }
        /**
         * 获取当前季度 起始时间
         * @return
         */
        public static Calendar getStartQuarter(Calendar today){
         int currentMonth = today.get(Calendar.MONTH) + 1; 
                 try { 
                    if (currentMonth >= 1 && currentMonth <= 3) 
                        today.set(Calendar.MONTH, 0); 
                    else if (currentMonth >= 4 && currentMonth <= 6) 
                        today.set(Calendar.MONTH, 3); 
                    else if (currentMonth >= 7 && currentMonth <= 9) 
                        today.set(Calendar.MONTH, 4); 
                    else if (currentMonth >= 10 && currentMonth <= 12) 
                        today.set(Calendar.MONTH, 9); 
                } catch (Exception e) { 
                    e.printStackTrace(); 
                } 
                return today;
        }
        /**
         * 获取当季的结束时间
         */
        public static Calendar getEndQuarter(Calendar today){
                int currentMonth = today.get(Calendar.MONTH) + 1; 
                try { 
                    if (currentMonth >= 1 && currentMonth <= 3) { 
                        today.set(Calendar.MONTH, 2); 
                        today.set(Calendar.DATE, 31); 
                    } else if (currentMonth >= 4 && currentMonth <= 6) { 
                        today.set(Calendar.MONTH, 5); 
                        today.set(Calendar.DATE, 30); 
                    } else if (currentMonth >= 7 && currentMonth <= 9) { 
                        today.set(Calendar.MONTH,8); 
                        today.set(Calendar.DATE, 30); 
                    } else if (currentMonth >= 10 && currentMonth <= 12) { 
                        today.set(Calendar.MONTH, 11); 
                        today.set(Calendar.DATE, 31); 
                    } 
                } catch (Exception e) { 
                    e.printStackTrace(); 
                } 
                return today; 
        }
        /**
         * 获取当年起始时间
         */
        public static Calendar getStartYear(Calendar today){
        try { 
                today.set(Calendar.MONTH, 0); 
                today.set(Calendar.DAY_OF_MONTH, today.getActualMinimum(Calendar.DAY_OF_MONTH)); 
        } catch (Exception e) { 
            e.printStackTrace(); 
        } 
        return today; 
        }
        /**
         * 获取当年结束时间
         */
        public static Calendar getEndYear(Calendar today){
                 try { 
                        today.set(Calendar.MONTH, 11); 
                    today.set(Calendar.DAY_OF_MONTH, today.getMaximum(Calendar.DAY_OF_MONTH)); 
              } catch (Exception e) { 
                    e.printStackTrace(); 
              } 
              return today; 
        }