Java Date类

• Date 类常见用法
• Date 和 String 的相互转换
• LocalDate

• 获取当前时间（Date中存放的是时间戳）

 Date today = new Date();
 System.out.println(today);

• 获取Date的部分信息（年、月、日）

Date date = new Date();
int dateDay = date.getDay();      

int dateYear = date.getYear();
int dateMonth = date.getMonth();
int dateDate = date.getDate();

int dateHour = date.getHours();
int dateMinute = date.getMinutes();
int dateSecond = date.getSeconds();

System.out.print(dateDay+"        "+dateYear+"/"+dateMonth+"/"+dateDate);
System.out.println("        "+ dateHour+"/"+dateMinute+"/"+dateSecond);

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
SimpleDateFormat sdf = new SimpleDateFormat("dd/M/yyyy");      
SimpleDateFormat sdf = new SimpleDateFormat("yyyy年MM月dd日 HH时mm分ss秒");

           
Date date = new Date();
String today = sdf.format(date);
System.out.println(today);

     


String  dateInString = today;
Date newDate = null;
try {
	newDate = sdf.parse(dateInString);
} catch (ParseException e) {
     
}
System.out.println(newDate);

 从Java 8之后，Java里面添加了许多的新特性，其中一个最常见也是最实用的便是日期处理的类——LocalDate。
新增的日期jar主要有三种：
java.time.LocalDate -> 只对年月日做出处理
java.time.LocalTime -> 只对时分秒纳秒做出处理
java.time.LocalDateTime -> 同时可以处理年月日和时分秒

 LocalDate today = LocalDate.now(); 
 System.out.println(today);
 int year = localDate.getYear();   
 int month = localDate.getMonthValue();       //6
 Month month2 = localDate.getMonth();         //"JUNE"
 int dayofMonth = today.getDayOfMonth();
 DayOfWeek dayofWeek = today.getDayOfWeek();
 
 
 LocalDate localDate = LocalDate.now();
 System.out.println("localDate: " + localDate);

 
 LocalTime localTime = LocalTime.now();
 System.out.println("localTime: " + localTime);
 
 
 LocalDateTime localDateTime = LocalDateTime.now();
 System.out.println("localDateTime: " + localDateTime);
 
 
 DateTimeFormatter formatter = DateTimeFormatter.ofPattern("YYYY-MM-dd HH:mm:ss");
 System.out.println("格式化之后的时间: " + localDateTime.format(formatter));