java 日期计算工具类小结

1、本周第一天： 

public static Date getStartTime4Week() throws Exception{      //SimpleDateFormat df=new SimpleDateFormat("yyyy-MM-dd");      Calendar cal = Calendar.getInstance();    int day_of_week = cal.get(Calendar.DAY_OF_WEEK) - 2;    cal.add(Calendar.DATE, -day_of_week);    /*String startTT = df.format(cal.getTime());    System.out.println("本周第一天: " + startTT);*/    return cal.getTime();}  

2、本周最后一天：

 public static Date getEndTime4Week() throws Exception{      //SimpleDateFormat df=new SimpleDateFormat("yyyy-MM-dd");      Calendar cal = Calendar.getInstance();    int day_of_week = cal.get(Calendar.DAY_OF_WEEK) - 2;    cal.add(Calendar.DATE, -day_of_week);    cal.add(Calendar.DATE, 6);    /*String startTT = df.format(cal.getTime());    System.out.println("本周第一天: " + startTT);*/    return cal.getTime();}  

3、本月第一天：

 public static Date getStartTime4Month() throws Exception{      //SimpleDateFormat df=new SimpleDateFormat("yyyy-MM-dd");    Calendar c = Calendar.getInstance();            c.add(Calendar.MONTH, 0);        c.set(Calendar.DAY_OF_MONTH,1);//设置为1号,当前日期既为本月第一天         //String first = df.format(c.getTime());        //System.out.println("===============first:"+first);        return c.getTime();}  

4、本月最后一天：

public static Date getEndTime4Month() throws Exception{      //SimpleDateFormat df=new SimpleDateFormat("yyyy-MM-dd");      Calendar ca = Calendar.getInstance();            ca.set(Calendar.DAY_OF_MONTH, ca.getActualMaximum(Calendar.DAY_OF_MONTH));          //String last = df.format(ca.getTime());        //System.out.println("===============last:"+last);    /*String startTT = df.format(cal.getTime());    System.out.println("本周第一天: " + startTT);*/    return ca.getTime();}

5、上月第一天：

<pre name="code" class="java">public static Date getStartTime4PreMonth() throws Exception{

<pre name="code" class="java">        Calendar   cal_1=Calendar.getInstance();//获取当前日期         cal_1.add(Calendar.MONTH, -1);        cal_1.set(Calendar.DAY_OF_MONTH,1);//设置为1号,当前日期既为本月第一天         firstDay = format.format(cal_1.getTime());        System.out.println("-----1------firstDay:"+firstDay);

return cal_1.getTime(); }

6、上月最后一天：

<pre name="code" class="java"><pre name="code" class="java">public static Date getStartTime4PreMonth() throws Exception{<span style="font-family: Arial, Helvetica, sans-serif;">       </span>

<pre name="code" class="java"><pre name="code" class="java">        Calendar cale = Calendar.getInstance();           cale.set(Calendar.DAY_OF_MONTH,0);//设置为1号,当前日期既为本月第一天         lastDay = format.format(cale.getTime());        System.out.println("-----2------lastDay:"+lastDay);

return cale.getTime();  

}

 
7、计算两个日期之间相差的天数 ：

public static int daysBetween(Date smdate,Date bdate) throws ParseException{            SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");          smdate=sdf.parse(sdf.format(smdate));          bdate=sdf.parse(sdf.format(bdate));          Calendar cal = Calendar.getInstance();            cal.setTime(smdate);            long time1 = cal.getTimeInMillis();                         cal.setTime(bdate);            long time2 = cal.getTimeInMillis();                 long between_days=(time2-time1)/(1000*3600*24);                     return Integer.parseInt(String.valueOf(between_days));               }    

 8、字符串的日期格式的计算：

public static int daysBetween(String smdate,String bdate) throws ParseException{          SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");          Calendar cal = Calendar.getInstance();            cal.setTime(sdf.parse(smdate));            long time1 = cal.getTimeInMillis();                         cal.setTime(sdf.parse(bdate));            long time2 = cal.getTimeInMillis();                 long between_days=(time2-time1)/(1000*3600*24);                     return Integer.parseInt(String.valueOf(between_days));     }

9、本季度第一天：

public static Date getStartTime4Quart() throws Exception{     SimpleDateFormat df=new SimpleDateFormat("yyyy-MM-dd");      Calendar c = Calendar.getInstance();        int currentMonth = c.get(Calendar.MONTH) + 1;        try {            if (currentMonth >= 1 && currentMonth <= 3)                c.set(Calendar.MONTH, 0);            else if (currentMonth >= 4 && currentMonth <= 6)                c.set(Calendar.MONTH, 3);            else if (currentMonth >= 7 && currentMonth <= 9)                c.set(Calendar.MONTH, 4);            else if (currentMonth >= 10 && currentMonth <= 12)                c.set(Calendar.MONTH, 9);            c.set(Calendar.DATE, 1);            System.out.println(df.format(c.getTime()));        } catch (Exception e) {            e.printStackTrace();        }        return c.getTime();    }  

10、本季度最后一天：

public static Date getEndTime4Quart() throws Exception{      SimpleDateFormat df=new SimpleDateFormat("yyyy-MM-dd");      Calendar c = Calendar.getInstance();        int currentMonth = c.get(Calendar.MONTH) + 1;        try {            if (currentMonth >= 1 && currentMonth <= 3) {                c.set(Calendar.MONTH, 2);                c.set(Calendar.DATE, 31);            } else if (currentMonth >= 4 && currentMonth <= 6) {                c.set(Calendar.MONTH, 5);                c.set(Calendar.DATE, 30);            } else if (currentMonth >= 7 && currentMonth <= 9) {                c.set(Calendar.MONTH, 8);                c.set(Calendar.DATE, 30);            } else if (currentMonth >= 10 && currentMonth <= 12) {                c.set(Calendar.MONTH, 11);                c.set(Calendar.DATE, 31);            }            System.out.println(df.format(c.getTime()));        } catch (Exception e) {            e.printStackTrace();        }        return c.getTime();    }  

11、本年第一天：

 public static Date getStartTime4Year() throws Exception{     SimpleDateFormat df=new SimpleDateFormat("yyyy-MM-dd");      Calendar c = Calendar.getInstance();        try {            c.set(Calendar.MONTH, 0);            c.set(Calendar.DATE, 1);            System.out.println(df.format(c.getTime()));        } catch (Exception e) {            e.printStackTrace();        }    return c.getTime();    } 

12、本年最后一天：

public static Date getEndTime4Year() throws Exception{      SimpleDateFormat df=new SimpleDateFormat("yyyy-MM-dd");      Calendar c = Calendar.getInstance();        try {            c.set(Calendar.MONTH, 11);            c.set(Calendar.DATE, 31);            System.out.println(df.format(c.getTime()));        } catch (Exception e) {            e.printStackTrace();        }    return c.getTime();    }

13、求两个日期之间的每一天

/**      * 获得日期字符串数组      * @param calendarType 日期跨度的类型，      * */            public static Date[] getDateArrays(Date start,Date end ,int calendarType){          ArrayList<Date> ret = new ArrayList<Date>();          Calendar calendar = Calendar.getInstance();          calendar.setTime(start);          Date tmpDate = calendar.getTime();          long endTime = end.getTime();          while(tmpDate.before(end)||tmpDate.getTime() == endTime){              ret.add(calendar.getTime());              calendar.add(calendarType, 1);              tmpDate = calendar.getTime();          }                           Date[] dates = new Date[ret.size()];          return ret.toArray(dates);            }    @Test      public void getDateArrays2(){          Date date = DateUtils.getDate("2008-04-01");          Date date2 = DateUtils.getDate("2008-08-01");          Date[] strArray = DateUtils.getDateArrays(date, date2, Calendar.DAY_OF_YEAR);          for (Date string : strArray) {              System.out.println(DateUtils.getDayStr(string));          }      }  

注：SimpleDateFormat是线程不安全的，放到类变量中需要注意。

参考文章：http://www.cnblogs.com/GYoungBean/archive/2012/10/31/2748219.html