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

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    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");

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运行结果如下