Java collection processing / null value processing / exception processing, use experience sharing!

Program ape Owen 2021-02-23 12:08:04
java collection processing null value

1. Arrays.asList

Business development , We often convert the original array to List Class data structure , To carry on with all kinds of Stream operation

  • Arrays.asList Cannot convert array of base type , have access to To switch
  • Arrays.asList Back to list Adding and deleting operations are not supported , It returned List yes Arrays The inner class of ArrayList. Internally inherited from AbstractList, There is no overriding parent add Method
  • The modification of the original array will affect the one we get List
    • ArrayList It's actually using the original array , So when you use it , It's best to reuse New ArrayList To decouple

2. Null processing

2.1 NullPointerException

  • Possible scenarios

    • The parameter value is Integer And so on , When using, there is an exception of null pointer due to automatic unpacking
    • String comparison
    • ConcurrentHashMap This container does not support Key and Value by null, Force put null Of key or Value A null pointer exception will occur
    • Method or remote service list yes null, Call directly without null , A null pointer exception occurred
    • Method of joint level call null check
  • best practice

    • string.equalsTo(variableName)
    • Optional.ofNullable()
    • orElse()

3. exception handling

3.1 Consider exception handling at the business code level

  • Most business applications adopt a three-tier architecture
    • Controller layer
      • Responsible for information collection , Parameter checking , Data adaptation front end of transformation service layer processing , Light business logic
      • Controller Capture exception , Then you need to give user-friendly tips
    • Service layer
      • Responsible for the core business logic , Including external service calls , Access database , Cache handling , Message processing, etc
      • It usually involves database transactions , Exception not suitable for capture , Otherwise, the transaction cannot be rolled back automatically
    • Repository layer
      • Responsible for data access implementation , Generally, there is no business logic
      • Do it according to the situation , Downgrade , Or turn it into a friendly exception
  • Exception handling at the framework level
    • Try not to do abnormal automation at the framework level , Unified treatment
    • The framework should do all the work , If the exception goes up to the top level and the logic still can't handle it , Exception conversion can be done in a unified way
      • @RestControllerAdvice
      • @ExceptionHandler

3.2 Don't eat it raw

After catching the exception, it should not be eaten raw , Because if the swallowing exception is not handled properly , appear Bug It's going to be hard to find .

There needs to be an appropriate transformation into a user-friendly exception , Or at least warn, error It's up to you log

3.3 Keep the original information

After catching the exception , Be sure to remember in log Or record the original exception information in the thrown out exception

catch (IOException e) { // Only exception messages are kept , There are no records on the stack log.error(" File read error , {}", e.getMessage()); throw new RuntimeException(" Please try again later ");}catch (IOException e) { throw new RuntimeException(" Please try again later ", e);}123456789

in addition , Focus on .........

本文为[Program ape Owen]所创,转载请带上原文链接,感谢

  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