2022/07/28 learning notes (day18) common APIs

JDK.API download ：

         link ：https://pan.baidu.com/s/1H0YYohJR198fODMWkrIC2Q 
         Extraction code ：6671 

API:

        1. What is? API：

        API（Application Programming Interface, Application programming interface ） Are some predefined functions , The purpose is to provide the ability for applications and developers to access a set of routines based on certain software or hardware , Without access to the source code , Or understand the details of the internal working mechanism .                                        

                                                                                                                                —— Baidu Encyclopedia

API(Application Programming Interface), That is, the application programming interface  

         2. How to use API

        a. Interface is introduced ：

         b. describe

         c. Construction method ：

         d. Member method ：

         

         Commonly used API：

API（Application Programming Interface） Application program interface

JDK Provide us with some classes that have been written , We can adjust the method directly to solve the problem

String（ It can be called API Interface ）

Methods of our class , Macroscopically, it can be called interface

      

Date class ：

Date：

 compareTo：

 

When you return a negative number , It indicates that the caller time is before the parameter time .

When to return to 0 when , It indicates that the caller time is the same as the parameter time .

When a positive number is returned , Explain that the caller's time is after the stated time .

Calendar class ： date 、 Time

Calendar Is an abstract class , can new Cannot create object

initialization ;

Provides a set of pairs “ Specific date 、 Minutes and seconds 、 week ” And other information operation functions . You can manipulate information in different time zones .

JDK1.1 Version start , When processing time and date , System recommended Calendar class

Calendar than Date Much more powerful

  Unless you want to get the month, day, hour, minute and second at one time , Otherwise, all use calendar

The time zone ：

ZoneId：

Date formatting ：

SimpleDateFormat：

        format： format Date type , hold Date Type into String type

         We want to show the data to the client

        parse： hold String Type of time , Turn into Date type

         The time transmitted from the client , It's usually String type , Store in database .

 

The duration of the Duration：

Get the current date LocalDate：

Determine if it's a leap year ：

 

Local time LocalTime：

Get day and time  LocalDateTime：

Deal with the formatting of dates  DateTimeFormatter：

hold Instant Turn into Date：

 

hold Date Turn into Instant：

hold Instant Turn into LocalDateTime：

  hold LocalDateTime Turn into Instant ：

hold Date Turn into LocalDateTime：

hold LocalDateTime Turn into Date：

 BigDecimal Statistics ：

Random classes Random：

Arrays—— Array tool class

Sort of array ：

Array search ：

 v 

  Array copy ：

Array comparison ：

System class —— System class  ：

Interview questions ： The difference between the three strings  ：