master

分支 (1)

管理

管理

master

blog
/
index.html

<!DOCTYPE html><html lang="zh-CN" data-theme="light"><head><meta charset="UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=edge"><meta name="viewport" content="width=device-width, initial-scale=1.0,viewport-fit=cover"><title>OrionLi's Blog</title><meta name="author" content="OrionLi"><meta name="copyright" content="OrionLi"><meta name="format-detection" content="telephone=no"><meta name="theme-color" content="#ffffff"><meta property="og:type" content="website">
<meta property="og:title" content="OrionLi&#39;s Blog">
<meta property="og:url" content="https://orionli.github.io/index.html">
<meta property="og:site_name" content="OrionLi&#39;s Blog">
<meta property="og:locale" content="zh_CN">
<meta property="og:image" content="https://avatars.githubusercontent.com/OrionLi">
<meta property="article:author" content="OrionLi">
<meta name="twitter:card" content="summary">
<meta name="twitter:image" content="https://avatars.githubusercontent.com/OrionLi"><link rel="shortcut icon" href="/img/favicon.png"><link rel="canonical" href="https://orionli.github.io/index.html"><link rel="preconnect" href="//cdn.jsdelivr.net"/><link rel="preconnect" href="//busuanzi.ibruce.info"/><link rel="stylesheet" href="/css/index.css"><link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/@fortawesome/fontawesome-free/css/all.min.css" media="print" onload="this.media='all'"><link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/@fancyapps/ui/dist/fancybox/fancybox.min.css" media="print" onload="this.media='all'"><script>const GLOBAL_CONFIG = {
  root: '/',
  algolia: undefined,
  localSearch: {"path":"/search.xml","preload":false,"top_n_per_article":1,"unescape":false,"languages":{"hits_empty":"找不到您查询的内容：${query}","hits_stats":"共找到 ${hits} 篇文章"}},
  translate: undefined,
  noticeOutdate: undefined,
  highlight: {"plugin":"highlighjs","highlightCopy":true,"highlightLang":true,"highlightHeightLimit":false},
  copy: {
    success: '复制成功',
    error: '复制错误',
    noSupport: '浏览器不支持'
  },
  relativeDate: {
    homepage: false,
    post: false
  },
  runtime: '天',
  dateSuffix: {
    just: '刚刚',
    min: '分钟前',
    hour: '小时前',
    day: '天前',
    month: '个月前'
  },
  copyright: undefined,
  lightbox: 'fancybox',
  Snackbar: undefined,
  source: {
    justifiedGallery: {
      js: 'https://cdn.jsdelivr.net/npm/flickr-justified-gallery/dist/fjGallery.min.js',
      css: 'https://cdn.jsdelivr.net/npm/flickr-justified-gallery/dist/fjGallery.min.css'
    }
  },
  isPhotoFigcaption: false,
  islazyload: false,
  isAnchor: false,
  percent: {
    toc: false,
    rightside: false,
  },
  autoDarkmode: true
}</script><script id="config-diff">var GLOBAL_CONFIG_SITE = {
  title: 'OrionLi\'s Blog',
  isPost: false,
  isHome: true,
  isHighlightShrink: false,
  isToc: false,
  postUpdate: '2023-12-18 14:38:41'
}</script><noscript><style type="text/css">
  #nav {
    opacity: 1
  }
  .justified-gallery img {
    opacity: 1
  }

  #recent-posts time,
  #post-meta time {
    display: inline !important
  }
</style></noscript><script>(win=>{
    win.saveToLocal = {
      set: function setWithExpiry(key, value, ttl) {
        if (ttl === 0) return
        const now = new Date()
        const expiryDay = ttl * 86400000
        const item = {
          value: value,
          expiry: now.getTime() + expiryDay,
        }
        localStorage.setItem(key, JSON.stringify(item))
      },

      get: function getWithExpiry(key) {
        const itemStr = localStorage.getItem(key)

        if (!itemStr) {
          return undefined
        }
        const item = JSON.parse(itemStr)
        const now = new Date()

        if (now.getTime() > item.expiry) {
          localStorage.removeItem(key)
          return undefined
        }
        return item.value
      }
    }

    win.getScript = url => new Promise((resolve, reject) => {
      const script = document.createElement('script')
      script.src = url
      script.async = true
      script.onerror = reject
      script.onload = script.onreadystatechange = function() {
        const loadState = this.readyState
        if (loadState && loadState !== 'loaded' && loadState !== 'complete') return
        script.onload = script.onreadystatechange = null
        resolve()
      }
      document.head.appendChild(script)
    })

    win.getCSS = (url,id = false) => new Promise((resolve, reject) => {
      const link = document.createElement('link')
      link.rel = 'stylesheet'
      link.href = url
      if (id) link.id = id
      link.onerror = reject
      link.onload = link.onreadystatechange = function() {
        const loadState = this.readyState
        if (loadState && loadState !== 'loaded' && loadState !== 'complete') return
        link.onload = link.onreadystatechange = null
        resolve()
      }
      document.head.appendChild(link)
    })

      win.activateDarkMode = function () {
        document.documentElement.setAttribute('data-theme', 'dark')
        if (document.querySelector('meta[name="theme-color"]') !== null) {
          document.querySelector('meta[name="theme-color"]').setAttribute('content', '#0d0d0d')
        }
      }
      win.activateLightMode = function () {
        document.documentElement.setAttribute('data-theme', 'light')
        if (document.querySelector('meta[name="theme-color"]') !== null) {
          document.querySelector('meta[name="theme-color"]').setAttribute('content', '#ffffff')
        }
      }
      const t = saveToLocal.get('theme')

          const isDarkMode = window.matchMedia('(prefers-color-scheme: dark)').matches
          const isLightMode = window.matchMedia('(prefers-color-scheme: light)').matches
          const isNotSpecified = window.matchMedia('(prefers-color-scheme: no-preference)').matches
          const hasNoSupport = !isDarkMode && !isLightMode && !isNotSpecified

          if (t === undefined) {
            if (isLightMode) activateLightMode()
            else if (isDarkMode) activateDarkMode()
            else if (isNotSpecified || hasNoSupport) {
              const now = new Date()
              const hour = now.getHours()
              const isNight = hour <= 7 || hour >= 20
              isNight ? activateDarkMode() : activateLightMode()
            }
            window.matchMedia('(prefers-color-scheme: dark)').addListener(function (e) {
              if (saveToLocal.get('theme') === undefined) {
                e.matches ? activateDarkMode() : activateLightMode()
              }
            })
          } else if (t === 'light') activateLightMode()
          else activateDarkMode()

      const asideStatus = saveToLocal.get('aside-status')
      if (asideStatus !== undefined) {
        if (asideStatus === 'hide') {
          document.documentElement.classList.add('hide-aside')
        } else {
          document.documentElement.classList.remove('hide-aside')
        }
      }

    const detectApple = () => {
      if(/iPad|iPhone|iPod|Macintosh/.test(navigator.userAgent)){
        document.documentElement.classList.add('apple')
      }
    }
    detectApple()
    })(window)</script><meta name="generator" content="Hexo 7.0.0"></head><body><div id="sidebar"><div id="menu-mask"></div><div id="sidebar-menus"><div class="avatar-img is-center"><img src="https://avatars.githubusercontent.com/OrionLi" onerror="onerror=null;src='/img/friend_404.gif'" alt="avatar"/></div><div class="sidebar-site-data site-data is-center"><a href="/archives/"><div class="headline">文章</div><div class="length-num">18</div></a><a href="/tags/"><div class="headline">标签</div><div class="length-num">15</div></a><a href="/categories/"><div class="headline">分类</div><div class="length-num">8</div></a></div><hr class="custom-hr"/><div class="menus_items"><div class="menus_item"><a class="site-page" href="/"><i class="fa-fw fas fa-home"></i><span> 首页</span></a></div><div class="menus_item"><a class="site-page" href="/categories/"><i class="fa-fw fas fa-folder-open"></i><span> 分类</span></a></div><div class="menus_item"><a class="site-page" href="/tags/"><i class="fa-fw fas fa-tags"></i><span> 标签</span></a></div><div class="menus_item"><a class="site-page" href="/archives/"><i class="fa-fw fas fa-archive"></i><span> 时间轴</span></a></div><div class="menus_item"><a class="site-page" href="/about/"><i class="fa-fw fas fa-heart"></i><span> 关于</span></a></div></div></div></div><div class="page" id="body-wrap"><header class="not-top-img" id="page-header"><nav id="nav"><span id="blog-info"><a href="/" title="OrionLi's Blog"><span class="site-name">OrionLi's Blog</span></a></span><div id="menus"><div id="search-button"><a class="site-page social-icon search" href="javascript:void(0);"><i class="fas fa-search fa-fw"></i><span> 搜索</span></a></div><div class="menus_items"><div class="menus_item"><a class="site-page" href="/"><i class="fa-fw fas fa-home"></i><span> 首页</span></a></div><div class="menus_item"><a class="site-page" href="/categories/"><i class="fa-fw fas fa-folder-open"></i><span> 分类</span></a></div><div class="menus_item"><a class="site-page" href="/tags/"><i class="fa-fw fas fa-tags"></i><span> 标签</span></a></div><div class="menus_item"><a class="site-page" href="/archives/"><i class="fa-fw fas fa-archive"></i><span> 时间轴</span></a></div><div class="menus_item"><a class="site-page" href="/about/"><i class="fa-fw fas fa-heart"></i><span> 关于</span></a></div></div><div id="toggle-menu"><a class="site-page" href="javascript:void(0);"><i class="fas fa-bars fa-fw"></i></a></div></div></nav></header><main class="layout" id="content-inner"><div class="recent-posts" id="recent-posts"><div class="recent-post-item"><div class="recent-post-info no-cover"><a class="article-title" href="/2023/09/15/guava-guide/" title="Guava常用工具类总结">Guava常用工具类总结</a><div class="article-meta-wrap"><span class="post-meta-date"><i class="fas fa-history"></i><span class="article-meta-label">更新于</span><time datetime="2023-09-15T07:58:00.000Z" title="更新于 2023-09-15 15:58:00">2023-09-15</time></span><span class="article-meta"><span class="article-meta-separator">|</span><i class="fas fa-inbox"></i><a class="article-meta__categories" href="/categories/%E5%AE%9E%E7%94%A8%E5%B7%A5%E5%85%B7/">实用工具</a></span><span class="article-meta tags"><span class="article-meta-separator">|</span><i class="fas fa-tag"></i><a class="article-meta__tags" href="/tags/%E4%BB%A3%E7%A0%81%E7%BE%8E%E5%AD%A6/">代码美学</a><span class="article-meta-link">•</span><a class="article-meta__tags" href="/tags/Guava/">Guava</a></span></div><div class="content">
原文链接：https://www.cnblogs.com/cuzzz/p/16609775.html


“我想写得更优雅，可是没人告诉我怎么写得更优雅”
“Null的含糊语义让人很不舒服。Null很少可以明确地表示某种语义，例如，Map.get(key)返回Null时，可能表示map中的值是null，亦或map中没有key对应的值。Null可以表示失败、成功或几乎任何情况。使用Null以外的特定值，会让你的逻辑描述变得更清晰。”

此文档只是Guava最常用工具介绍，guava存在更多本文档没有介绍的api

OptionalOptional类是Java8为了解决null值判断问题，借鉴google guava类库的Optional类而引入的一个同名Optional类，使用Optional类可以避免显式的null值判断（null的防御性检查），避免null导致的NPE（NullPointerException）。

这里讲的optional 也是指jdk中的optional，其实二者类似，但是编码使用gauva的optional，阿里巴巴编程规范会提醒换成jdk自带的optio ...</div></div></div><div class="recent-post-item"><div class="recent-post-info no-cover"><a class="article-title" href="/2023/09/10/turing-assessment/" title="图灵考核路线">图灵考核路线</a><div class="article-meta-wrap"><span class="post-meta-date"><i class="fas fa-history"></i><span class="article-meta-label">更新于</span><time datetime="2023-09-10T12:00:00.000Z" title="更新于 2023-09-10 20:00:00">2023-09-10</time></span><span class="article-meta"><span class="article-meta-separator">|</span><i class="fas fa-inbox"></i><a class="article-meta__categories" href="/categories/%E5%AD%A6%E4%B9%A0%E8%B7%AF%E7%BA%BF/">学习路线</a></span><span class="article-meta tags"><span class="article-meta-separator">|</span><i class="fas fa-tag"></i><a class="article-meta__tags" href="/tags/%E5%AD%A6%E4%B9%A0%E8%B7%AF%E7%BA%BF/">学习路线</a></span></div><div class="content">本文介绍图灵智能创新团队各方向学习路线和考核内容</div></div></div><div class="recent-post-item"><div class="recent-post-info no-cover"><a class="article-title" href="/2023/09/07/avoid-bugs/" title="防坑集锦">防坑集锦</a><div class="article-meta-wrap"><span class="post-meta-date"><i class="fas fa-history"></i><span class="article-meta-label">更新于</span><time datetime="2023-09-07T13:31:00.000Z" title="更新于 2023-09-07 21:31:00">2023-09-07</time></span><span class="article-meta"><span class="article-meta-separator">|</span><i class="fas fa-inbox"></i><a class="article-meta__categories" href="/categories/%E9%98%85%E8%AF%BB/">阅读</a></span><span class="article-meta tags"><span class="article-meta-separator">|</span><i class="fas fa-tag"></i><a class="article-meta__tags" href="/tags/%E9%98%B2%E5%9D%91%E9%9B%86%E9%94%A6/">防坑集锦</a></span></div><div class="content">谨慎使用@Builder大多数同学使用 @Builder 无非就是为了链式编程，然而 @Builder 并不是链式编程的最佳实践，它会额外创建内部类，存在继承关系时还需要使用 @SuperBuilder 注解，设置默认值时也需要额外的 @Builder.Default 去设置默认值，无疑增加了很多不必要的复杂度。
为什么（1）@Builder 生成的构造器不是完美的，它不能区分哪些参数是必须的，哪些是可选的。如果没有提供必须的参数，构造器可能会创建出不完整或者不合法的对象。

@Builder 注解产生的 Builder 类的构造方法默认并不能限定必传参数。

（2）很多人 喜欢 @Builder 和 @Data 搭配使用，导致生成的构造器是可变的，它允许使用 setter 方法修改构造器的状态。这违反了构造器模式的原则，构造器应该是不可变的，一旦创建就不能被修改。

如果非要使用 @Builder ，那么不要用 @Data ，要用 @Getter。相对来说，反而 @Accessors 的行为更符合这个要求。

（3）@Builder 生成的构造器不适合用于短暂的对象，它会增加代码的复 ...</div></div></div><div class="recent-post-item"><div class="recent-post-info no-cover"><a class="article-title" href="/2023/09/07/Improve-write-performance/" title="(四)提升系统的“读”性能">(四)提升系统的“读”性能</a><div class="article-meta-wrap"><span class="post-meta-date"><i class="fas fa-history"></i><span class="article-meta-label">更新于</span><time datetime="2023-09-07T13:03:00.000Z" title="更新于 2023-09-07 21:03:00">2023-09-07</time></span><span class="article-meta"><span class="article-meta-separator">|</span><i class="fas fa-inbox"></i><a class="article-meta__categories" href="/categories/%E6%9E%B6%E6%9E%84%E5%AD%A6%E4%B9%A0/">架构学习</a></span><span class="article-meta tags"><span class="article-meta-separator">|</span><i class="fas fa-tag"></i><a class="article-meta__tags" href="/tags/%E6%9E%B6%E6%9E%84%E8%AE%BE%E8%AE%A1/">架构设计</a></span></div><div class="content">缓存本地缓存
比如Caffeine


缓存不太容易变化的数据（保障缓存一致性）

缓存数据量较小的数据（不会受到内存的限制）
如元数据、配置数据：启动的时候，从DB加载到内存的缓存块里。这样每次读这些数据的时候，就不用访问DB了


中心化缓存
比如Redis


针对用户请求相关数据的缓存
用户流量触发的DB的数据（查询）
业务计算的数据
返回结果的数据


缓存更新策略cache aside pattern（经典缓存更新策略）采用的是写数据时删除缓存中旧值，读数据时更新新值
但如果有一个读请求和一个写请求几乎同时到达DB
读请求先访问数据库，将（旧）值写入缓存时有些延迟
而写请求后访问数据库（新值），但把缓存删完了，读请求才开始写入缓存
这就造成缓存数据是旧的
解决方案
保证即使把旧值更新到cache的情况，在后面的某一个时间点也能淘汰掉有问题的缓存


  sequenceDiagram
    Server-&gt;&gt;Database: 1.写入数据

    Server-&gt;&gt;Cache: 2.删除缓存

    Server-&gt;&gt;Datab ...</div></div></div><div class="recent-post-item"><div class="recent-post-info no-cover"><a class="article-title" href="/2023/09/05/carry-the-flow/" title="(三)如何提高代码的扩展性">(三)如何提高代码的扩展性</a><div class="article-meta-wrap"><span class="post-meta-date"><i class="fas fa-history"></i><span class="article-meta-label">更新于</span><time datetime="2023-09-06T07:30:00.000Z" title="更新于 2023-09-06 15:30:00">2023-09-06</time></span><span class="article-meta"><span class="article-meta-separator">|</span><i class="fas fa-inbox"></i><a class="article-meta__categories" href="/categories/%E6%9E%B6%E6%9E%84%E5%AD%A6%E4%B9%A0/">架构学习</a></span><span class="article-meta tags"><span class="article-meta-separator">|</span><i class="fas fa-tag"></i><a class="article-meta__tags" href="/tags/%E6%9E%B6%E6%9E%84%E8%AE%BE%E8%AE%A1/">架构设计</a><span class="article-meta-link">•</span><a class="article-meta__tags" href="/tags/%E4%BB%A3%E7%A0%81%E7%BE%8E%E5%AD%A6/">代码美学</a></span></div><div class="content">先来看一段代码
123456789101112131415161718192021222324252627282930313233343536373839404142434445/** * 转账服务 * * @param payer 付款方 * @param payee 收款方 * @param money 转账金额 * * @return 是否转账成功 */public boolean transfer(String payer, String payee, String money) &#123;    Log.info(&quot;transfer start, payer = &quot; + payer + &quot;, payee = &quot; + payee + &quot;, money = &quot; + money);    // 1. 检查参数    if (!isValidUser(payer) || !isValidUser(payee) || !isValidMoney(money)) &#123;        return false;    & ...</div></div></div><div class="recent-post-item"><div class="recent-post-info no-cover"><a class="article-title" href="/2023/09/03/process-engine/" title="(二)搭完架子串珠子——流程引擎">(二)搭完架子串珠子——流程引擎</a><div class="article-meta-wrap"><span class="post-meta-date"><i class="fas fa-history"></i><span class="article-meta-label">更新于</span><time datetime="2023-09-03T08:00:00.000Z" title="更新于 2023-09-03 16:00:00">2023-09-03</time></span><span class="article-meta"><span class="article-meta-separator">|</span><i class="fas fa-inbox"></i><a class="article-meta__categories" href="/categories/%E6%9E%B6%E6%9E%84%E5%AD%A6%E4%B9%A0/">架构学习</a></span><span class="article-meta tags"><span class="article-meta-separator">|</span><i class="fas fa-tag"></i><a class="article-meta__tags" href="/tags/%E6%9E%B6%E6%9E%84%E8%AE%BE%E8%AE%A1/">架构设计</a><span class="article-meta-link">•</span><a class="article-meta__tags" href="/tags/%E4%BB%A3%E7%A0%81%E7%BE%8E%E5%AD%A6/">代码美学</a></span></div><div class="content">单用模板方法带来的问题1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950public UserInfoDTO getUserInfo(@RequestParam(&quot;userId&quot;) String userId) &#123;    return (new ServiceTemplate&lt;String&gt;() &#123;        @Override        public void validParam(String request) &#123;            // 1. 校验入参            if (userId == null || userId.isEmpty()) &#123;                throw new RuntimeException(&quot;param UserId is invalid&quot;);            &#125;        &# ...</div></div></div><div class="recent-post-item"><div class="recent-post-info no-cover"><a class="article-title" href="/2023/09/02/template-method/" title="(一)搭系统先搭架子——模板方法模式">(一)搭系统先搭架子——模板方法模式</a><div class="article-meta-wrap"><span class="post-meta-date"><i class="fas fa-history"></i><span class="article-meta-label">更新于</span><time datetime="2023-09-02T14:36:00.000Z" title="更新于 2023-09-02 22:36:00">2023-09-02</time></span><span class="article-meta"><span class="article-meta-separator">|</span><i class="fas fa-inbox"></i><a class="article-meta__categories" href="/categories/%E6%9E%B6%E6%9E%84%E5%AD%A6%E4%B9%A0/">架构学习</a></span><span class="article-meta tags"><span class="article-meta-separator">|</span><i class="fas fa-tag"></i><a class="article-meta__tags" href="/tags/%E6%9E%B6%E6%9E%84%E8%AE%BE%E8%AE%A1/">架构设计</a><span class="article-meta-link">•</span><a class="article-meta__tags" href="/tags/%E4%BB%A3%E7%A0%81%E7%BE%8E%E5%AD%A6/">代码美学</a><span class="article-meta-link">•</span><a class="article-meta__tags" href="/tags/%E8%AE%BE%E8%AE%A1%E6%A8%A1%E5%BC%8F/">设计模式</a></span></div><div class="content">引例——抽取工具类先来看看这段代码：
12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455@GetMapping(path = &quot;/getUserInfo&quot;)public UserInfoDTO getUserInfo(@RequestParam(&quot;userId&quot;) String userId) &#123;    // 1. 打印入口日志    logger.info(&quot;userId: &quot; + userId + &quot; visit path: /getUserInfo&quot;);    try &#123;        // 2. 检验入参合理性，userId是否以字母&#x27;u&#x27;开头。正确的uid示例：u001        if (userId == null || !userId.startsWith(&quot;u&quot;)) &#123; ...</div></div></div><div class="recent-post-item"><div class="recent-post-info no-cover"><a class="article-title" href="/2023/08/12/code-aesthetic/" title="代码美学">代码美学</a><div class="article-meta-wrap"><span class="post-meta-date"><i class="fas fa-history"></i><span class="article-meta-label">更新于</span><time datetime="2023-08-16T10:13:00.000Z" title="更新于 2023-08-16 18:13:00">2023-08-16</time></span><span class="article-meta"><span class="article-meta-separator">|</span><i class="fas fa-inbox"></i><a class="article-meta__categories" href="/categories/%E4%BB%A3%E7%A0%81%E7%BE%8E%E5%AD%A6/">代码美学</a></span><span class="article-meta tags"><span class="article-meta-separator">|</span><i class="fas fa-tag"></i><a class="article-meta__tags" href="/tags/%E4%BB%A3%E7%A0%81%E7%BE%8E%E5%AD%A6/">代码美学</a></span></div><div class="content">在代码中命名避免使用单个字母命名数学家以简洁为荣，他们爱把表达式浓缩成最精简的模式。
问题在于你不用编辑数学式子，但需要编辑代码
因为一个字母无法体现一个变量的相关信息
绝对不要缩写缩写的含意依赖于上下文，而你并不总是了解这个上下文。这就会造成读代码的时间可能比写代码的时间还多
因此强行让自己去理解各种不同的命名方式，只会让阅读陌生代码更加困难
既然现在我们有了会自动补全的IDE和大屏幕，为什么不把名字写完整些？
在变量名中带上单位比如说你有一个接收延迟时间为参数的函数
1void execute(int delay)

如果这个值的单位为秒
1void execute(int delaySeconds)

这样这个函数的用户就能明白，应该传入秒数为参数
同时也让编辑这个类的人能够明白，这个函数用的是什么单位
当然，更好的做法是使用枚举，这样用户就不用关心具体的单位
12345678@Getterpublic enum Delay &#123;    SECONDS_1(1),    SECONDS_5(5),    SECONDS_10(10),        private fin ...</div></div></div><div class="recent-post-item"><div class="recent-post-info no-cover"><a class="article-title" href="/2023/08/05/backend-guide/" title="后端入门">后端入门</a><div class="article-meta-wrap"><span class="post-meta-date"><i class="fas fa-history"></i><span class="article-meta-label">更新于</span><time datetime="2023-08-05T07:00:00.000Z" title="更新于 2023-08-05 15:00:00">2023-08-05</time></span><span class="article-meta"><span class="article-meta-separator">|</span><i class="fas fa-inbox"></i><a class="article-meta__categories" href="/categories/%E5%AD%A6%E4%B9%A0%E8%B7%AF%E7%BA%BF/">学习路线</a></span><span class="article-meta tags"><span class="article-meta-separator">|</span><i class="fas fa-tag"></i><a class="article-meta__tags" href="/tags/%E5%AD%A6%E4%B9%A0%E8%B7%AF%E7%BA%BF/">学习路线</a></span></div><div class="content">本文主要介绍了后端的概念和Java学习路线的指导</div></div></div><div class="recent-post-item"><div class="recent-post-info no-cover"><a class="article-title" href="/2023/07/25/go-note1/" title="(一)Go基本语法">(一)Go基本语法</a><div class="article-meta-wrap"><span class="post-meta-date"><i class="fas fa-history"></i><span class="article-meta-label">更新于</span><time datetime="2023-07-25T14:09:00.000Z" title="更新于 2023-07-25 22:09:00">2023-07-25</time></span><span class="article-meta"><span class="article-meta-separator">|</span><i class="fas fa-inbox"></i><a class="article-meta__categories" href="/categories/%E4%BB%A5Java%E8%A7%86%E8%A7%92%E5%AD%A6Go/">以Java视角学Go</a></span><span class="article-meta tags"><span class="article-meta-separator">|</span><i class="fas fa-tag"></i><a class="article-meta__tags" href="/tags/Go/">Go</a><span class="article-meta-link">•</span><a class="article-meta__tags" href="/tags/%E5%AD%97%E8%8A%82%E8%B7%B3%E5%8A%A8%E9%9D%92%E8%AE%AD%E8%90%A5/">字节跳动青训营</a></span></div><div class="content">变量变量声明显式声明
如果我们未为一个变量初始化，则必须显式指定变量类型

如果声明时不指定具体的值，则会被赋值为默认值。


12var str string // str的值为&quot;&quot;(空字符串)var num int    // num的值为0

快速声明赋值
Go 支持变量类型自动推断，也就是说，当我们立即为一个变量进行初始化时，其类型是可以省略的

可以通过 := 符号以一种简单的方式（也是实际上最常用的方式）声明一个变量


12a, b := 1, 2// Go 支持多个变量在同一行同时声明str := &quot;我是字符串。&quot;

常量声明可以使用 const 关键字代替 var 关键字来创建一个常量（不可变变量）
12345const str string = &quot;我是字符串&quot;const num int = 1const a, b = 3, 4num = 2 // 若更改会报错

流程控制if
Go的if语句和C、Java类似，只不过if后面没有括号，但是加上括号也能正确运行
if后面的开始大括号必须跟if在同一行，不能换行 ...</div></div></div><nav id="pagination"><div class="pagination"><span class="page-number current">1</span><a class="page-number" href="/page/2/#content-inner">2</a><a class="extend next" rel="next" href="/page/2/#content-inner"><i class="fas fa-chevron-right fa-fw"></i></a></div></nav></div><div class="aside-content" id="aside-content"><div class="card-widget card-info"><div class="is-center"><div class="avatar-img"><img src="https://avatars.githubusercontent.com/OrionLi" onerror="this.onerror=null;this.src='/img/friend_404.gif'" alt="avatar"/></div><div class="author-info__name">OrionLi</div><div class="author-info__description"></div></div><div class="card-info-data site-data is-center"><a href="/archives/"><div class="headline">文章</div><div class="length-num">18</div></a><a href="/tags/"><div class="headline">标签</div><div class="length-num">15</div></a><a href="/categories/"><div class="headline">分类</div><div class="length-num">8</div></a></div><a id="card-info-btn" target="_blank" rel="noopener" href="https://github.com/OrionLi"><i class="fab fa-github"></i><span>Follow Me</span></a><div class="card-info-social-icons is-center"><a class="social-icon" href="https://github.com/OrionLi" target="_blank" title="Github"><i class="fab fa-github" style="color: #24292e;"></i></a><a class="social-icon" href="mailto:jw4hbp1d1@mozmail.com" target="_blank" title="Email"><i class="fas fa-envelope" style="color: #4a7dbe;"></i></a></div></div><div class="sticky_layout"><div class="card-widget card-webinfo"><div class="item-headline"><i class="fas fa-chart-line"></i><span>网站资讯</span></div><div class="webinfo"><div class="webinfo-item"><div class="item-name">文章数目 :</div><div class="item-count">18</div></div><div class="webinfo-item"><div class="item-name">已运行时间 :</div><div class="item-count" id="runtimeshow" data-publishDate="2023-06-19T16:00:00.000Z"><i class="fa-solid fa-spinner fa-spin"></i></div></div><div class="webinfo-item"><div class="item-name">本站访客数 :</div><div class="item-count" id="busuanzi_value_site_uv"><i class="fa-solid fa-spinner fa-spin"></i></div></div><div class="webinfo-item"><div class="item-name">本站总访问量 :</div><div class="item-count" id="busuanzi_value_site_pv"><i class="fa-solid fa-spinner fa-spin"></i></div></div><div class="webinfo-item"><div class="item-name">最后更新时间 :</div><div class="item-count" id="last-push-date" data-lastPushDate="2023-12-18T06:38:40.917Z"><i class="fa-solid fa-spinner fa-spin"></i></div></div></div></div></div></div></main><footer id="footer"><div id="footer-wrap"><div class="copyright">&copy;2023 By OrionLi</div><div class="framework-info"><span>框架 </span><a target="_blank" rel="noopener" href="https://hexo.io">Hexo</a><span class="footer-separator">|</span><span>主题 </span><a target="_blank" rel="noopener" href="https://github.com/jerryc127/hexo-theme-butterfly">Butterfly</a></div></div></footer></div><div id="rightside"><div id="rightside-config-hide"><button id="darkmode" type="button" title="浅色和深色模式转换"><i class="fas fa-adjust"></i></button><button id="hide-aside-btn" type="button" title="单栏和双栏切换"><i class="fas fa-arrows-alt-h"></i></button></div><div id="rightside-config-show"><button id="rightside_config" type="button" title="设置"><i class="fas fa-cog fa-spin"></i></button><button id="go-up" type="button" title="回到顶部"><span class="scroll-percent"></span><i class="fas fa-arrow-up"></i></button></div></div><div><script src="/js/utils.js"></script><script src="/js/main.js"></script><script src="https://cdn.jsdelivr.net/npm/@fancyapps/ui/dist/fancybox/fancybox.umd.min.js"></script><script>function panguFn () {
  if (typeof pangu === 'object') pangu.autoSpacingPage()
  else {
    getScript('https://cdn.jsdelivr.net/npm/pangu/dist/browser/pangu.min.js')
      .then(() => {
        pangu.autoSpacingPage()
      })
  }
}

function panguInit () {
  if (false){
    GLOBAL_CONFIG_SITE.isPost && panguFn()
  } else {
    panguFn()
  }
}

document.addEventListener('DOMContentLoaded', panguInit)</script><div class="js-pjax"><script>(() => {
  const $mermaid = document.querySelectorAll('#article-container .mermaid-wrap')
  if ($mermaid.length === 0) return
  const runMermaid = () => {
    window.loadMermaid = true
    const theme = document.documentElement.getAttribute('data-theme') === 'dark' ? 'dark' : 'default'

    Array.from($mermaid).forEach((item, index) => {
      const mermaidSrc = item.firstElementChild
      const mermaidThemeConfig = '%%{init:{ \'theme\':\'' + theme + '\'}}%%\n'
      const mermaidID = 'mermaid-' + index
      const mermaidDefinition = mermaidThemeConfig + mermaidSrc.textContent

      const renderFn = mermaid.render(mermaidID, mermaidDefinition)

      const renderV10 = () => {
        renderFn.then(({svg}) => {
          mermaidSrc.insertAdjacentHTML('afterend', svg)
        })
      }

      const renderV9 = svg => {
        mermaidSrc.insertAdjacentHTML('afterend', svg)
      }

      typeof renderFn === 'string' ? renderV9(renderFn) : renderV10()
    })
  }

  const loadMermaid = () => {
    window.loadMermaid ? runMermaid() : getScript('https://cdn.jsdelivr.net/npm/mermaid/dist/mermaid.min.js').then(runMermaid)
  }

  btf.addModeChange('mermaid', runMermaid)

  window.pjax ? loadMermaid() : document.addEventListener('DOMContentLoaded', loadMermaid)
})()</script></div><canvas class="fireworks" mobile="false"></canvas><script src="https://cdn.jsdelivr.net/npm/butterfly-extsrc/dist/fireworks.min.js"></script><script async data-pjax src="//busuanzi.ibruce.info/busuanzi/2.3/busuanzi.pure.mini.js"></script><div id="local-search"><div class="search-dialog"><nav class="search-nav"><span class="search-dialog-title">搜索</span><span id="loading-status"></span><button class="search-close-button"><i class="fas fa-times"></i></button></nav><div class="is-center" id="loading-database"><i class="fas fa-spinner fa-pulse"></i><span>  数据库加载中</span></div><div class="search-wrap"><div id="local-search-input"><div class="local-search-box"><input class="local-search-box--input" placeholder="搜索文章" type="text"/></div></div><hr/><div class="no-result" id="local-search-results"></div><div id="local-search-stats-wrap"></div></div></div><div id="search-mask"></div><script src="/js/search/local-search.js"></script></div></div></body></html>