Simpledateformat class and list interface

User 8211341 2021-04-16 18:10:08
simpledateformat class list interface


Hello everyone , I am a Java Initiate , Today, Xiao Bian will take you to study together Java Technology base !

One 、SimpleDateFormat class

1.SimpleDateFormat Class is DateFormat Subclasses of classes . If you use DateFormat Class does not meet the requirements , Then use its subclass , It can go through new Keyword to create the object , The constructor takes a string parameter , Represents its date format . It's a format that allows you to choose any user-defined date and time .

2. Date and time format encoding , Here's the picture :

The picture is quoted from 《 Novice tutorial 》

3.SimpleDateFormat Class formats the current date and outputs an example of a statement :

import java.text.SimpleDateFormat;
import java.util.Date;
public class p4 {
public static void main(String[] args) {
// TODO Auto-generated method stub
// Create a Date object
Date d=new Date();
// Create a SimpleDateFormat object
SimpleDateFormat s=new SimpleDateFormat(" It's today "+"Gyyyy year MM month dd Japan :HH spot mm branch ss second ,yyyy In the first D God ");
// hold SimpleDateFormat Object conversion to Date object
System.out.println(s.format(d));
}
}

The result of the operation is :

From the above code ,G It's a sign of an era , four yyyy Indicates the year , Such as 2020 year ; If it's two yy It means the year , Such as 20;MM It means the month , Such as 10;dd Days , Such as 24;HH It's the number of hours , Such as 09;mm Represents the number of minutes , Such as 46;ss Represents the number of seconds , Such as 09;D Day of the year , Such as 298.

Two 、List Interface

( One )List It's an ordered set 、 Repeatable sets . It's inheritance Collection Interface , stay List There are elements in a collection that can be duplicated , By index ( Subscript ) To access elements in the specified location . Another is the order of elements , It sets the index in element order , The first one is added to List The index value of the element of the collection is 0, The second one is added to List The index value of the element of the collection is 1, By analogy .

( Two ) Realization List Interface , It mainly has two commonly used classes, namely ArrayList class 、LinkedList class .

1.ArrayList Class is List An implementation class of the interface , In its ArrayList Class implements the size of variable length arrays , The data stored in it is the element . When the stored element exceeds its length ,ArrayList Allocate a large array in memory to store these elements , So it's the size of a variable length array .

2.LinkedList Class is a collection, adding and deleting elements are more efficient , This set maintains a bidirectional circular linked list , Each element in the linked list can be referenced to record the previous element and the next element , Just connect all the elements together .

3、 ... and 、JDK5.0 New characteristics --foreach loop

1.foreach Cycle is for A special simplified version of the statement , however foreach Statements cannot be completely replaced for sentence , Any foreach Statements can be rewritten to for sentence . Usually used to traverse the elements of an array or collection .

2.foreach Cyclic syntax format :

for( Element type Element variables : Traversal object ){
Execute statement
}

3.foreach Examples of cycles :

import java.util.ArrayList;
public class p5 {
public static void main(String[] args) {
// TODO Auto-generated method stub
// establish ArrayList aggregate
ArrayList l = new ArrayList();
// Add elements to the collection
l.add("java actual combat ");
l.add("C Language ");
l.add(" The principle and application of database ");
l.add(" data structure ");
//foreach Loop traversal ArrayList object
for(Object o : l){
System.out.println(o);
}
}
}

The result of the operation is :

From the above code , Use foreach It's convenient to loop through all the elements of the collection , There is no cyclic condition , The number of cycles is the number of elements , When every cycle , Write down the elements of the current loop through its element variables , And then output the elements of the set .

Four 、 summary

This paper mainly introduces SimpleDateFormat class 、List Interface 、JDK5.0 New characteristics --foreach loop .

SimpleDateFormat Class is an abstract class , The constructor takes a string parameter , Represents its current date format . It's a format that allows you to choose any user-defined date and time , Introduced its date and time format coding .

Realization List Interface , It mainly has two commonly used classes, namely ArrayList class 、LinkedList class .

foreach Circulation brings convenience to developers , It's usually used to traverse the elements of arrays and collections .

I am a Java Initiate , I hope you can learn from this article , It helps you ! Welcome to WeChat , If you have any problems, you can help us solve them at any time , It's good to make a friend ~

This article is from WeChat official account. - Java Advanced learning communication (java_xianghong) , author :Java Initiate

The source and reprint of the original text are detailed in the text , If there is any infringement , Please contact the [email protected] Delete .

Original publication time : 2021-04-08

Participation of this paper Tencent cloud media sharing plan , You are welcome to join us , share .

版权声明
本文为[User 8211341]所创,转载请带上原文链接,感谢
https://javamana.com/2021/04/20210416162503296v.html

  1. 【计算机网络 12(1),尚学堂马士兵Java视频教程
  2. 【程序猿历程,史上最全的Java面试题集锦在这里
  3. 【程序猿历程(1),Javaweb视频教程百度云
  4. Notes on MySQL 45 lectures (1-7)
  5. [computer network 12 (1), Shang Xuetang Ma soldier java video tutorial
  6. The most complete collection of Java interview questions in history is here
  7. [process of program ape (1), JavaWeb video tutorial, baidu cloud
  8. Notes on MySQL 45 lectures (1-7)
  9. 精进 Spring Boot 03:Spring Boot 的配置文件和配置管理,以及用三种方式读取配置文件
  10. Refined spring boot 03: spring boot configuration files and configuration management, and reading configuration files in three ways
  11. 精进 Spring Boot 03:Spring Boot 的配置文件和配置管理,以及用三种方式读取配置文件
  12. Refined spring boot 03: spring boot configuration files and configuration management, and reading configuration files in three ways
  13. 【递归,Java传智播客笔记
  14. [recursion, Java intelligence podcast notes
  15. [adhere to painting for 386 days] the beginning of spring of 24 solar terms
  16. K8S系列第八篇(Service、EndPoints以及高可用kubeadm部署)
  17. K8s Series Part 8 (service, endpoints and high availability kubeadm deployment)
  18. 【重识 HTML (3),350道Java面试真题分享
  19. 【重识 HTML (2),Java并发编程必会的多线程你竟然还不会
  20. 【重识 HTML (1),二本Java小菜鸟4面字节跳动被秒成渣渣
  21. [re recognize HTML (3) and share 350 real Java interview questions
  22. [re recognize HTML (2). Multithreading is a must for Java Concurrent Programming. How dare you not
  23. [re recognize HTML (1), two Java rookies' 4-sided bytes beat and become slag in seconds
  24. 造轮子系列之RPC 1:如何从零开始开发RPC框架
  25. RPC 1: how to develop RPC framework from scratch
  26. 造轮子系列之RPC 1:如何从零开始开发RPC框架
  27. RPC 1: how to develop RPC framework from scratch
  28. 一次性捋清楚吧,对乱糟糟的,Spring事务扩展机制
  29. 一文彻底弄懂如何选择抽象类还是接口,连续四年百度Java岗必问面试题
  30. Redis常用命令
  31. 一双拖鞋引发的血案,狂神说Java系列笔记
  32. 一、mysql基础安装
  33. 一位程序员的独白:尽管我一生坎坷,Java框架面试基础
  34. Clear it all at once. For the messy, spring transaction extension mechanism
  35. A thorough understanding of how to choose abstract classes or interfaces, baidu Java post must ask interview questions for four consecutive years
  36. Redis common commands
  37. A pair of slippers triggered the murder, crazy God said java series notes
  38. 1、 MySQL basic installation
  39. Monologue of a programmer: despite my ups and downs in my life, Java framework is the foundation of interview
  40. 【大厂面试】三面三问Spring循环依赖,请一定要把这篇看完(建议收藏)
  41. 一线互联网企业中,springboot入门项目
  42. 一篇文带你入门SSM框架Spring开发,帮你快速拿Offer
  43. 【面试资料】Java全集、微服务、大数据、数据结构与算法、机器学习知识最全总结,283页pdf
  44. 【leetcode刷题】24.数组中重复的数字——Java版
  45. 【leetcode刷题】23.对称二叉树——Java版
  46. 【leetcode刷题】22.二叉树的中序遍历——Java版
  47. 【leetcode刷题】21.三数之和——Java版
  48. 【leetcode刷题】20.最长回文子串——Java版
  49. 【leetcode刷题】19.回文链表——Java版
  50. 【leetcode刷题】18.反转链表——Java版
  51. 【leetcode刷题】17.相交链表——Java&python版
  52. 【leetcode刷题】16.环形链表——Java版
  53. 【leetcode刷题】15.汉明距离——Java版
  54. 【leetcode刷题】14.找到所有数组中消失的数字——Java版
  55. 【leetcode刷题】13.比特位计数——Java版
  56. oracle控制用户权限命令
  57. 三年Java开发,继阿里,鲁班二期Java架构师
  58. Oracle必须要启动的服务
  59. 万字长文!深入剖析HashMap,Java基础笔试题大全带答案
  60. 一问Kafka就心慌?我却凭着这份,图灵学院vip课程百度云