JavaDev | 一如Java深似海

[Java 杂记] 表驱动法和 if-else，switch-case 优化

What is a "table-driven method"?

什么叫表驱动法表驱动法，又称之为表驱动、表驱动方法。“表”是几乎所有数据结构课本都要讨论的非常有用的数据结构。表驱动方法出于特定的目的来使用表，程序员们经常谈到“表驱动”方法，但是课本中却从未提到过什么是“表驱动”方法。来自 Google 的解释：表驱动法是一种编程模式，它的本质是，从表里查询信息来代替逻辑语句（if,case）。先来看个案例：通过月份来获取当月的天数（仅作为案例演示，......

Posted by Mr.Vincent on 2020-11-11

Java 杂记

[Calling Third-party API - Java API] 2 Core Java APIs for making Java http requests

A URLConnection with support for HTTP-specific features. An HttpClient can be used to send requests and retrieve their responses...

Since Java 1.1 there has been an HTTP client in the core libraries provided with the JDK. With Java 11 a new client was added. One of these might be a good choice if you are sensitive about adding ......

Posted by Mr.Vincent on 2020-11-07

Calling Third-party API

[Calling Third-party API] 1 How to call Third-party API

Making HTTP requests is a core feature of modern programming, and is often one of the first things you want to do when learning a new programming language. For Java programmers there are many ways to do it - core libraries in the JDK and third-party libraries...

概述我们在日常开发过程中，有不少场景会对接第三方的 API，例如第三方账号登录，第三方服务等等。第三方服务会提供 API 或者 SDK，早些年 Maven 还没那么广泛使用，通常要对接第三方服务的时候会去下载第三方服务的 SDK 开发包，也就是 jar 包，拷贝到自己的工程中进行开发。但现如今，几乎所有的大中小企业都使用 Maven 进行依赖管理，第三方服务通过提供 SDK 包的情况越来越......

Posted by Mr.Vincent on 2020-11-07

Calling Third-party API

[Mac] Mac 刷新 DNS 缓存

Reset the DNS cache in OS X...

根据 Mac OS X 操作系统的版本选择以下命令： Mac OS X 12 (Sierra) and later 123sudo killall -HUP mDNSRespondersudo killall mDNSResponderHelpersudo dscacheutil -flushcache Mac OS X 11 (El Capitan) and OS X 12 (Sierra......

Posted by Mr.Vincent on 2020-11-07

Mac

[POI - Alibaba EasyExcel] Alibaba EasyExcel

EasyExcel is a simple, memory-saving open source project for reading and writing Excel based on Java...

简介 Java 领域解析、生成 Excel 比较有名的框架有 Apache poi、jxl 等。但他们都存在一个严重的问题就是非常的耗内存。如果你的系统并发量不大的话可能还行，但是一旦并发上来后一定会 OOM 或者 JVM 频繁的 full gc。EasyExcel 是阿里巴巴开源的一个 excel 处理框架，以使用简单、节省内存著称。EasyExcel 是一个基于 Java 的简单、省内存......

Posted by Mr.Vincent on 2020-10-22

POI

[POI - Apache POI] Apache POI

The Apache POI project is the master project for developing pure Java ports of file formats based on Microsoft's OLE 2 Compound Document Format...

概述 Apache POI 是基于 Office Open XML标准（OOXML）和 Microsoft 的 OLE 2 复合文档格式（OLE2）处理各种文件格式的开源项目。简而言之，您可以使用 Java 读写 MS Excel 文件，也可以使用 Java 读写 MS Word 和 MS PowerPoint 文件。官网：https://poi.apache.org/ 在线 Javad......

Posted by Mr.Vincent on 2020-10-22

POI

[MQ - RabbitMQ] 1 消息队列

什么是 MQ Message Queue（MQ），消息队列中间件。很多人都说：MQ 通过将消息的发送和接收分离来实现应用程序的异步和解偶，这个给人的直觉是——MQ 是异步的，用来解耦的，但是这个只是 MQ 的效果而不是目的。MQ 真正的目的是为了通讯，屏蔽底层复杂的通讯协议，定义了一套应用层的、更加简单的通讯协议。一个分布式系统中两个模块之间通讯要么是 HTTP，要么是自己开发的 TCP，但......

Posted by Mr.Vincent on 2020-10-14

MQ

[Ubuntu] 4.1 Ubuntu 安装 OpenJDK 11

OpenJDK (Open Java Development Kit) is a free and open-source implementation of the Java Platform, Standard Edition (Java SE)...

开始之前有很多不同的 Java 实现。OpenJDK 和 Oracle Java 是最主要的两个 Java 实现，除了 Oracle Java 拥有极少的一些额外特性之外，它们两个基本没有什么不同。 Oracle Java 授权仅仅允许作为非商业软件的使用，例如：个人用途和开发用途。默认的 Ubuntu 20.04 源仓库包含了两个 OpenJDK 软件包，, Java Runtime ......

Posted by Mr.Vincent on 2020-10-14

Ubuntu

[Ubuntu] Ubuntu Server（18.04、20.04）安装

Ubuntu is the modern, open source operating system on Linux for the enterprise server, desktop, cloud, and IoT...

下载官网下载：https://releases.ubuntu.com/20.04/?C=M;O=A 安装概述 Ubuntu Server 是您已经知道的标准 Ubuntu 的变体，专为网络和服务量身定制。它与在50,000个节点的云中运行一样，能够运行简单的文件服务器。与 Ubuntu Desktop 的安装不同，Ubuntu Server 不包含图形安装程序。相反，它使用基于文本菜单......

Posted by Mr.Vincent on 2020-10-13

Ubuntu

[Linux] VMware 虚拟机三种网络模式详解

VMware Workstation Pro is the industry standard desktop hypervisor for running virtual machines on Linux or Windows PCs...

概述由于 Linux 目前很热门，越来越多的人在学习 Linux，但是买一台服务放家里来学习，实在是很浪费。那么如何解决这个问题？虚拟机软件是很好的选择，常用的虚拟机软件有 VMware Workstations、Virtual Box、Parallels Desktop（for Mac）等。在使用虚拟机软件的时候，很多初学者都会遇到很多问题，而 VMware 的网络连接问题是大家遇到最......

Posted by Mr.Vincent on 2020-10-13

Linux

Live My Life

[Java 杂记] 表驱动法和 if-else，switch-case 优化

What is a "table-driven method"?

[Calling Third-party API - Java API] 2 Core Java APIs for making Java http requests

A URLConnection with support for HTTP-specific features. An HttpClient can be used to send requests and retrieve their responses...

[Calling Third-party API] 1 How to call Third-party API

Making HTTP requests is a core feature of modern programming, and is often one of the first things you want to do when learning a new programming language. For Java programmers there are many ways to do it - core libraries in the JDK and third-party libraries...

[Mac] Mac 刷新 DNS 缓存

Reset the DNS cache in OS X...

[POI - Alibaba EasyExcel] Alibaba EasyExcel

EasyExcel is a simple, memory-saving open source project for reading and writing Excel based on Java...

[POI - Apache POI] Apache POI

The Apache POI project is the master project for developing pure Java ports of file formats based on Microsoft's OLE 2 Compound Document Format...

[MQ - RabbitMQ] 1 消息队列

[Ubuntu] 4.1 Ubuntu 安装 OpenJDK 11

OpenJDK (Open Java Development Kit) is a free and open-source implementation of the Java Platform, Standard Edition (Java SE)...

[Ubuntu] Ubuntu Server（18.04、20.04）安装

Ubuntu is the modern, open source operating system on Linux for the enterprise server, desktop, cloud, and IoT...

[Linux] VMware 虚拟机三种网络模式详解

VMware Workstation Pro is the industry standard desktop hypervisor for running virtual machines on Linux or Windows PCs...

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