1 主函数

 public static void main(String[] args) {int number = 10;System.out.println(toInt(toBytes(number)));}

2 int转化成byte

 public static byte[] toBytes(int number){byte[] bytes = new byte[4];bytes[0] = (byte)number;bytes[1] = (byte) (number >> 8);bytes[2] = (byte) (number >> 16);bytes[3] = (byte) (number >> 24);return bytes;}

3 byte转化成int

 public static int toInt(byte[] bytes){int number = 0;for(int i = 0; i < 4 ; i++){number += bytes[i] << i*8;}return number;}

4 测试结果

5 过程分析

int占4个字节；byte占1个字节。int转化成byte的时候每次取低八位，用四个byte来存储一个int的值。byte转化成int的时候再按原来逆向移动相同的位数并叠加。

6 知识延伸

• 移位操作
  https://blog.csdn.net/zhangyong01245/article/details/83715717
• 源码、反码、补码
  正数：
  反码是源码
  补码是源码
  负数：
  反码是源码除符号位都取反
  补码是反码加1
• 计算机为什么要用补码表示数值
  https://blog.csdn.net/leonliu06/article/details/78685197

                                </div><link href="https://csdnimg.cn/release/phoenix/mdeditor/markdown_views-b6c3c6d139.css" rel="stylesheet"><div class="more-toolbox"><div class="left-toolbox"><ul class="toolbox-list"><li class="tool-item tool-active is-like "><a href="javascript:;"><svg class="icon" aria-hidden="true"><use xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#csdnc-thumbsup"></use></svg><span class="name">点赞</span><span class="count"></span></a></li><li class="tool-item tool-active is-collection "><a href="javascript:;" data-report-click="{&quot;mod&quot;:&quot;popu_824&quot;}"><svg class="icon" aria-hidden="true"><use xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#icon-csdnc-Collection-G"></use></svg><span class="name">收藏</span></a></li><li class="tool-item tool-active is-share"><a href="javascript:;"><svg class="icon" aria-hidden="true"><use xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#icon-csdnc-fenxiang"></use></svg>分享</a></li><!--打赏开始--><!--打赏结束--><li class="tool-item tool-more"><a><svg t="1575545411852" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="5717" xmlns:xlink="http://www.w3.org/1999/xlink" width="200" height="200"><defs><style type="text/css"></style></defs><path d="M179.176 499.222m-113.245 0a113.245 113.245 0 1 0 226.49 0 113.245 113.245 0 1 0-226.49 0Z" p-id="5718"></path><path d="M509.684 499.222m-113.245 0a113.245 113.245 0 1 0 226.49 0 113.245 113.245 0 1 0-226.49 0Z" p-id="5719"></path><path d="M846.175 499.222m-113.245 0a113.245 113.245 0 1 0 226.49 0 113.245 113.245 0 1 0-226.49 0Z" p-id="5720"></path></svg></a><ul class="more-box"><li class="item"><a class="article-report">文章举报</a></li></ul></li></ul></div></div><div class="person-messagebox"><div class="left-message"><a href="https://blog.csdn.net/qq_41637061"><img src="https://profile.csdnimg.cn/1/B/8/3_qq_41637061" class="avatar_pic" username="qq_41637061"><img src="https://g.csdnimg.cn/static/user-reg-year/1x/2.png" class="user-years"></a></div><div class="middle-message"><div class="title"><span class="tit"><a href="https://blog.csdn.net/qq_41637061" data-report-click="{&quot;mod&quot;:&quot;popu_379&quot;}" target="_blank">李白的诗</a></span></div><div class="text"><span>发布了53 篇原创文章</span> · <span>获赞 6</span> · <span>访问量 20万+</span></div></div><div class="right-message"><a href="https://im.csdn.net/im/main.html?userName=qq_41637061" target="_blank" class="btn btn-sm btn-red-hollow bt-button personal-letter">私信</a><a class="btn btn-sm  bt-button personal-watch" data-report-click="{&quot;mod&quot;:&quot;popu_379&quot;}">关注</a></div></div></div>