日期类型

Date

• 构造方法：new Date(long time) 将long型数据转为日期
• 普通方法：getTime(),返回一个long型日期

    // 输出日期
    Date date= new Date();
    System.out.println(date);
    long cur = date.getTime();

SimpleDateFormat类型用于日期的格式转换

• 构造函数：new SimpleDateFormat("日期格式")
• Date转String：String Format(Date date)
• String转Date：Date prase(String str)

public class test {
    public static void main(String[] args) throws ParseException {
        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS");
        Date date = new Date();
        String str = simpleDateFormat.format(date);
        System.out.println(str);
        date = simpleDateFormat.parse(str);
        System.out.println(date);
    }
}

Calendar日期类型主要用于计算

• 构造函数私有化
• 静态方法取得实例对象：getInstance()
• 静态属性：YEAR，MONTH，DAY_OF_MONTH，HOUR_OF_DAY，MINUTE，SECOND

public class test {
    public static void main(String[] args) throws ParseException {
        Calendar calendar = Calendar.getInstance();
        System.out.println(calendar.get(Calendar.YEAR));
        System.out.println(calendar.get(Calendar.MONTH));
        System.out.println(calendar.get(Calendar.DAY_OF_MONTH));
        System.out.println(calendar.get(Calendar.HOUR_OF_DAY));
        System.out.println(calendar.get(Calendar.MINUTE));
        System.out.println(calendar.get(Calendar.SECOND));
    }
}