java.util.Date

public class Date extends Object implements Serializable, Cloneable, Comparable<Date>

构造方法：

Constructor and Description
`Date()` Allocates a `Date` object and initializes it so that it represents the time at which it was allocated, measured to the nearest millisecond.
`Date(int year, int month, int date)`Deprecated. As of JDK version 1.1, replaced by `Calendar.set(year + 1900, month, date)` or `GregorianCalendar(year + 1900, month, date)`.
`Date(int year, int month, int date, int hrs, int min)`Deprecated. As of JDK version 1.1, replaced by `Calendar.set(year + 1900, month, date, hrs, min)` or `GregorianCalendar(year + 1900, month, date, hrs, min)`.
`Date(int year, int month, int date, int hrs, int min, int sec)`Deprecated. As of JDK version 1.1, replaced by `Calendar.set(year + 1900, month, date, hrs, min, sec)` or `GregorianCalendar(year + 1900, month, date, hrs, min, sec)`.
`Date(long date)` Allocates a `Date` object and initializes it to represent the specified number of milliseconds since the standard base time known as "the epoch", namely January 1, 1970, 00:00:00 GMT.
`Date(String s)`Deprecated. As of JDK version 1.1, replaced by `DateFormat.parse(String s)`.

常见方法：

Modifier and Type	Method and Description
`boolean`	`after(Date when)` Tests if this date is after the specified date.
`boolean`	`before(Date when)` Tests if this date is before the specified date.
`Object`	`clone()` Return a copy of this object.
`int`	`compareTo(Date anotherDate)` Compares two Dates for ordering.
`boolean`	`equals(Object obj)` Compares two dates for equality.
`int`	`getDate()`Deprecated. As of JDK version 1.1, replaced by `Calendar.get(Calendar.DAY_OF_MONTH)`.
`int`	`getDay()`Deprecated. As of JDK version 1.1, replaced by `Calendar.get(Calendar.DAY_OF_WEEK)`.
`int`	`getHours()`Deprecated. As of JDK version 1.1, replaced by `Calendar.get(Calendar.HOUR_OF_DAY)`.
`int`	`getMinutes()`Deprecated. As of JDK version 1.1, replaced by `Calendar.get(Calendar.MINUTE)`.
`int`	`getMonth()`Deprecated. As of JDK version 1.1, replaced by `Calendar.get(Calendar.MONTH)`.
`int`	`getSeconds()`Deprecated. As of JDK version 1.1, replaced by `Calendar.get(Calendar.SECOND)`.
`long`	`getTime()` Returns the number of milliseconds since January 1, 1970, 00:00:00 GMT represented by this Date object.
`int`	`getTimezoneOffset()`Deprecated. As of JDK version 1.1, replaced by `-(Calendar.get(Calendar.ZONE_OFFSET) + Calendar.get(Calendar.DST_OFFSET)) / (60 1000)`.*
`int`	`getYear()`Deprecated. As of JDK version 1.1, replaced by `Calendar.get(Calendar.YEAR) - 1900`.
`int`	`hashCode()` Returns a hash code value for this object.
`static long`	`parse(String s)`Deprecated. As of JDK version 1.1, replaced by `DateFormat.parse(String s)`.
`void`	`setDate(int date)`Deprecated. As of JDK version 1.1, replaced by `Calendar.set(Calendar.DAY_OF_MONTH, int date)`.
`void`	`setHours(int hours)`Deprecated. As of JDK version 1.1, replaced by `Calendar.set(Calendar.HOUR_OF_DAY, int hours)`.
`void`	`setMinutes(int minutes)`Deprecated. As of JDK version 1.1, replaced by `Calendar.set(Calendar.MINUTE, int minutes)`.
`void`	`setMonth(int month)`Deprecated. As of JDK version 1.1, replaced by `Calendar.set(Calendar.MONTH, int month)`.
`void`	`setSeconds(int seconds)`Deprecated. As of JDK version 1.1, replaced by `Calendar.set(Calendar.SECOND, int seconds)`.
`void`	`setTime(long time)` Sets this `Date` object to represent a point in time that is `time` milliseconds after January 1, 1970 00:00:00 GMT.
`void`	`setYear(int year)`Deprecated. As of JDK version 1.1, replaced by `Calendar.set(Calendar.YEAR, year + 1900)`.
`String`	`toGMTString()`Deprecated. As of JDK version 1.1, replaced by `DateFormat.format(Date date)`, using a GMT `TimeZone`.
`String`	`toLocaleString()`Deprecated. As of JDK version 1.1, replaced by `DateFormat.format(Date date)`.
`String`	`toString()` Converts this `Date` object to a `String` of the form:
`static long`	`UTC(int year, int month, int date, int hrs, int min, int sec)`Deprecated. As of JDK version 1.1, replaced by `Calendar.set(year + 1900, month, date, hrs, min, sec)` or `GregorianCalendar(year + 1900, month, date, hrs, min, sec)`, using a UTC `TimeZone`, followed by `Calendar.getTime().getTime()`.

学习笔记：

所有的数据类型在计算机中都以数字的形式表现出来，日期也不例外。其中最特殊的就是零。0代表java中的时间原点，对应的日期是1970年8点0分0秒。所有的日期，都以这个0点为基准，每过1毫秒，就+1.

getTime() 得到一个long型的整数
这个整数代表从1970.1.1 08:00:00:000 开始每经历一毫秒，增加1.

当前日期的毫秒数
new Date().getTime() 和 System.currentTimeMillis() 是一样的
不过由于机器性能的原因，可能会相差几十毫秒，毕竟每执行一行代码，都是需要时间的

创建日期对象

JAVA_Date学习笔记

日期格式化 SimpleDateFormat

y 代表年

M 代表月

d 代表日

H 代表24进制的小时

h 代表12进制的小时

m 代表分钟

s 代表秒

S 代表毫秒

JAVA_Date学习笔记

Calendar类

即日历类，常用于进行“翻日历”，比如下个月的今天是多久。

The Calendar class is an abstract class that provides methods for converting between a specific instant in time and a set of calendar fields such as YEAR, MONTH, DAY_OF_MONTH, HOUR, and so on, and for manipulating the calendar fields, such as getting the date of the next week. An instant in time can be represented by a millisecond value that is an offset from the Epoch, January 1, 1970 00:00:00.000 GMT (Gregorian).

采用单例模式获取日历对象Calendar.getInstance();

JAVA_Date学习笔记

主要学习了java.util包下面的和时间有关的几个类。

JAVA_Date学习笔记

java.util.Date

构造方法：

常见方法：

学习笔记：

日期格式化 SimpleDateFormat

Calendar类

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