Java日期时间处理-优快云博客

本文链接：https://blog.youkuaiyun.com/qq_34707150/article/details/98759169

本文详细介绍如何使用Java进行日期和时间的获取、格式化以及日期的解析，并演示了如何利用Calendar类进行日期操作，包括获取时间的各个部分、计算日期所在周数及月份天数等。

//获取时间方法1
Date d = new Date();//获取当前时间
DateFormat df = new SimpleDateFormat("yyyy-MM-dd");
System.out.println(df.format(d));//将日期转换为String格式

//获取时间方法2
String time = "2019-08-10";//传入自定义时间
DateFormat df = new SimpleDateFormat("yyyy-MM-dd");
Date d = null;
try {
    d = df.parse(time);
} catch (ParseException e) {
    e.printStackTrace();
}

//下方都是针对方法1和2的处理
System.out.println("当前时间毫秒数：" + d.getTime());
System.out.println("当前时间毫秒数：" + System.currentTimeMillis());

Calendar calendar = Calendar.getInstance();
calendar.setTime(d);//将Date传给calendar
System.out.println("当前时间毫秒数：" + calendar.getTimeInMillis());
System.out.println(calendar.get(Calendar.YEAR) + "年");
System.out.println((calendar.get(Calendar.MONTH) + 1) + "月");
System.out.println(calendar.get(Calendar.DATE) + "日");
System.out.println(getWeek(calendar.get(Calendar.DAY_OF_WEEK)));
System.out.println("当年第" + calendar.get(Calendar.WEEK_OF_YEAR) + "周");
System.out.println("当月第" + calendar.get(Calendar.WEEK_OF_MONTH) + "周");
System.out.println("当月最大日期数为" + calendar.getMaximum(Calendar.DATE));
System.out.println("当月最大日期数为" + calendar.getActualMaximum(Calendar.DATE));
System.out.println("日期:" + calendar.getTime());

private static String getWeek(int dayForWeek) {    String week;
    switch (dayForWeek) {
        case Calendar.SUNDAY://1周日
            week = "周日";
            break;
        case Calendar.MONDAY://2周一
            week = "周一";
            break;
        case Calendar.TUESDAY://3周二
            week = "周二";
            break;
        case Calendar.WEDNESDAY://4周三
            week = "周三";
            break;
        case Calendar.THURSDAY://5周四
            week = "周四";
            break;
        case Calendar.FRIDAY://6周五
            week = "周五";
            break;
        case Calendar.SATURDAY://7周六
            week = "周六";
            break;
        default:
            week = "错误";
            break;
    }
    return week;
}

打印指定月份的日期表

public static void main(String[] args) {
    Date date=new Date();
    DateFormat df=new SimpleDateFormat("yyyy-MM-dd");
    Calendar calendar=Calendar.getInstance();
    System.out.println(df.format(date)+"\t"+getWeek(calendar.get(Calendar.DAY_OF_WEEK)));
    System.out.println("日\t一\t二\t三\t四\t五\t六");
    int maxDay=calendar.getActualMaximum(Calendar.DATE);
    int nowDay=calendar.get(Calendar.DATE);
    calendar.set(Calendar.DATE,1);//设置日期，从1号开始
    for (int i = 1; i <calendar.get(Calendar.DAY_OF_WEEK) ; i++) {
        System.out.print("\t");
    }
    for (int i = 1; i <= maxDay; i++) {
        if(nowDay==i){
            System.out.print("*");
        }
        System.out.print(i+"\t");
        if(calendar.get(Calendar.DAY_OF_WEEK)==Calendar.SATURDAY){
            System.out.println();
        }
        calendar.add(Calendar.DATE,1);//日期加1
    }
}

效果如下：