java的Calendar类

最新推荐文章于 2023-09-04 10:40:41 发布

ShanRui_

最新推荐文章于 2023-09-04 10:40:41 发布

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本文详细介绍 Java 中 Calendar 类的使用方法，包括如何获取日期组件、设置日期、计算日期差及获取当天、当周和当月的日期范围等。通过具体代码示例展示了 Calendar 类的强大功能。

ava中的Calendar在开发中经常被忽略，这篇博客总结一下这个类，对后面项目中使用时期的时候有帮助。

Calendar常量（field）的作用

Calendar cal = Calendar.getInstance();
cal.get(Calendar.DATE);//-----------------------当天 1-31
cal.get(Calendar.DAY_OF_MONTH);//---------------当天 1-31
cal.get(Calendar.DAY_OF_WEEK);//----------------从星期天开始计算，如果今天星期二，那么返回3
cal.get(Calendar.DAY_OF_YEAR);//----------------
cal.get(Calendar.HOUR);//-----------------------12小时制
cal.get(Calendar.HOUR_OF_DAY);//----------------24小时制，一般使用这个属性赋值
cal.get(Calendar.MILLISECOND);//----------------
cal.get(Calendar.MINUTE);//---------------------
cal.get(Calendar.SECOND);//---------------------
cal.get(Calendar.WEEK_OF_MONTH);//--------------
cal.get(Calendar.WEEK_OF_YEAR);//---------------
cal.get(Calendar.MONTH);//-----------------------月份获取需要 +1，那么，赋值时需要 -1

总结：
1）常量的真正意义如上，我们一般使用这些常量进行赋值，换句话说，可以通过它获取值同样可以通过它进行对应赋值
2）赋值时，week 与 month 是很值得注意的，week 需要指定 setFirstDayOfWeek ， 然而，月份则需要加减 1
3）赋值时，我们一般采用 年 月 日 时 分 秒 
Calendar.YEAR 、Calendar.MONTH 、Calendar.DAY_OF_MONTH、 Calendar.HOUR_OF_DAY 、Calendar.MINUTE、 Calendar.SECOND

主要赋值语句

 cal.set(Calendar.XXX, VVVV);//--------------------- 对以上每个字段（field）进行赋值，代码重复较大
 cal.set(year,month,date,hour,minute,second);//----- 分别对字段（field）进行赋值，效率高

主要计算

 cal1.roll(Calendar.MONTH,3);//---------------------- 一般不使用，原因是该方法只在一个月里面循环计算，其大小不会超过该月最值
 cal1.add(Calendar.YEAR,-1);//----------------------- 使用 XX_OF_XX 的field进行加减计算效果更佳，而且计算准确
 cal1.add(field,value);//----------------------------

总结：
    1）关于roll的计算，cal.roll(Calendar.DAY_OF_MONTH, 32);虽然32已经超出了最大的可能31，但是cal实际是不会超出该月的，而是把32减去该月天数之后，重新计算剩下的天数；
    2）关于add的计算，cal1.add(Calendar.MONTH, 1); 如果当前为8-31，那么，加一个月的话就是9-30，这个才是真正的准确

主要取值语句

    cal.getMaximum(Calendar.DATE);
    cal.get(Calendar.DATE);
    cal.getMinimum(Calendar.DATE);
    cal.setTimeInMillis(cal.getTime().getTime());
    cal.setTimeInMillis(new Date().getTime());
总结：
    1）获取最大值，最小值是很常用的方法
    2）获取毫秒数后，可以通过 1000*60*60 进行计算

Calendar 获取当天\当月\当周

<code class="hljs sql has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">// 当天
    public String getThisToday(){
            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        Calendar cal = Calendar.getInstance();
        cal.<span class="hljs-operator" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">set</span>(Calendar.HOUR_OF_DAY,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>);</span>
        cal.<span class="hljs-operator" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">set</span>(Calendar.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">MINUTE</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>);</span>
        cal.<span class="hljs-operator" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">set</span>(Calendar.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">SECOND</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>);</span>
        String <span class="hljs-operator" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">start</span> = sdf.format(cal.getTime());</span>
        cal.<span class="hljs-operator" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">set</span>(Calendar.HOUR_OF_DAY,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">23</span>);</span>
        cal.<span class="hljs-operator" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">set</span>(Calendar.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">MINUTE</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">59</span>);</span>
        cal.<span class="hljs-operator" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">set</span>(Calendar.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">SECOND</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">59</span>);</span>
        String <span class="hljs-operator" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">end</span> = sdf.format(cal.getTime());</span>
        return <span class="hljs-operator" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">start</span>+<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"|"</span>+<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">end</span>;</span>
    }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li></ul>

<code class="hljs sql has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">// 本周
     public String getThisWeekDate(){
             SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
            Calendar ca = Calendar.getInstance();
            ca.setFirstDayOfWeek(Calendar.MONDAY);
            ca.<span class="hljs-operator" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">set</span>(Calendar.DAY_OF_WEEK,Calendar.SUNDAY);</span>
    ca.<span class="hljs-operator" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">set</span>(ca.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">get</span>(Calendar.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">YEAR</span>), ca.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">get</span>(Calendar.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">MONTH</span>),ca.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">get</span>(Calendar.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">DATE</span>),<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">23</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">59</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">59</span>);</span>
            String <span class="hljs-operator" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">end</span> = sdf.format(ca.getTime());</span>
            ca.<span class="hljs-operator" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">set</span>(Calendar.DAY_OF_WEEK, Calendar.MONDAY);</span>
            ca.<span class="hljs-operator" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">set</span>(Calendar.HOUR_OF_DAY,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>);</span>
            ca.<span class="hljs-operator" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">set</span>(Calendar.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">MINUTE</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>);</span>
            ca.<span class="hljs-operator" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">set</span>(Calendar.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">SECOND</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>);</span>
            String <span class="hljs-operator" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">start</span> = sdf.format(ca.getTime());</span>
            return <span class="hljs-operator" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">start</span>+<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"|"</span>+<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">end</span>;</span>
      }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li></ul>

<code class="hljs sql has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">//本月日期段
        public String getThisMonthDate(){
         SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        Calendar cc2 = Calendar.getInstance();
        int maxMonthDay = cc2.getActualMaximum(Calendar.DAY_OF_MONTH);
        cc2.<span class="hljs-operator" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">set</span>(cc2.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">get</span>(Calendar.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">YEAR</span>), cc2.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">get</span>(Calendar.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">MONTH</span>),maxMonthDay,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">23</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">59</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">59</span>);</span>
        String <span class="hljs-operator" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">end</span> = sdf.format(cc2.getTime());</span>
        cc2.<span class="hljs-operator" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">set</span>(cc2.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">get</span>(Calendar.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">YEAR</span>), cc2.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">get</span>(Calendar.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">MONTH</span>),<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>);</span>
        String <span class="hljs-operator" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">start</span> = sdf.format(cc2.getTime());</span>
        return <span class="hljs-operator" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">start</span>+<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"|"</span>+<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">end</span>;</span>
        }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li></ul>