calendar 时间类

给大家介绍下calendar 这个时间类吧，通常如果用到时间的话，就免不了需要用到这个类，希望大家有用

下面是代码，直接拿到main方法里面可以直接运行

--------------------------------------

    SimpleDateFormat format = new SimpleDateFormat(\"yyyy-MM-dd HH:mm:ss\");
    SimpleDateFormat format1 = new SimpleDateFormat(\"yyyy-MM-dd\");

    Calendar calendar = Calendar.getInstance();
    calendar.set(Calendar.DAY_OF_MONTH,1);
    System.out.println(format1.format(calendar.getTime()) + \"这月第一天\");

    System.out.println( format1.format(Calendar.getInstance().getTime()) + \"当天\");

    System.out.println( format.format(Calendar.getInstance().getTime()) + \"现在\");

    calendar = Calendar.getInstance();
    calendar.set(Calendar.MONTH,0);
    calendar.set(Calendar.DAY_OF_MONTH,1);
    System.out.println(format1.format(calendar.getTime()) + \"今年第一天\");

    calendar = Calendar.getInstance();
    calendar.set(Calendar.DAY_OF_WEEK,2);
    System.out.println(format1.format(calendar.getTime()) + \"这周第一天(星期一)\");

    calendar = Calendar.getInstance();
    calendar.add(Calendar.MONTH,-1);
    calendar.set(Calendar.DAY_OF_MONTH,1);
    System.out.println(format1.format(calendar.getTime()) + \"上月第一天\");

    calendar = Calendar.getInstance();
    calendar.set(Calendar.DAY_OF_MONTH,0);
    System.out.println(format1.format(calendar.getTime()) + \"上月最后一天\");

    calendar = Calendar.getInstance();
    calendar.add(Calendar.MONTH,-2);
    calendar.set(Calendar.DAY_OF_MONTH,1);
    System.out.println(format1.format(calendar.getTime()) + \"上上月第一天\");

    calendar = Calendar.getInstance();
    calendar.add(Calendar.MONTH,-1);
    calendar.set(Calendar.DAY_OF_MONTH,0);
    System.out.println(format1.format(calendar.getTime()) + \"上上月最后一天\");

    calendar = Calendar.getInstance();
    calendar.add(Calendar.YEAR,-1);
    calendar.add(Calendar.MONTH,-1);
    calendar.set(Calendar.DAY_OF_MONTH,1);
    System.out.println(format1.format(calendar.getTime()) + \"去年上月第一天\");

    calendar = Calendar.getInstance();
    calendar.add(Calendar.YEAR,-1);
    calendar.set(Calendar.DAY_OF_MONTH,0);
    System.out.println(format1.format(calendar.getTime()) + \"去年上月最后一天\");

--------------------

运行结果如下