小编use*_*672的帖子

例如,我有一个Processor基类,其方法返回一个Object并将Object作为参数.我想扩展它并创建一个StringProcessor,它将返回String并将String作为参数.但是,协变类型只允许返回值,但不允许参数.这种限制的原因是什么？

class Processor {
    Object process (Object input) {
        //create a copy of input, modify it and return it
        return copy;
    }
}

class StringProcessor extends Processor {
    @Override
    String process (String input) { // permitted for parameter. why?
        //create a copy of input string, modify it and return it
        return copy;
    }
}

使用以下 HTML，如何仅选择父级的所有 div，但带有属性的 div 除外 -class="first"及其使用 JavaScript 的子级？

换句话说，在调用查询后，我想获得一个包含以下 div 的数组：class="all",class="second"和class="third"。

<div class="all">
    <div class="header">All</div>
    <div class="cell-1"></div>
    <div class="cell-2"></div>
    <div class="cell-3"></div>
    <div class="cell-4"></div>
</div>
<div class="first">
    <div class="header">First</div>
    <div class="cell-1"></div>
    <div class="cell-2"></div>
    <div class="cell-3"></div>
    <div class="cell-4"></div>
</div>
<div class="second">
    <div class="header">Second</div>
    <div class="cell-1"></div>
    <div class="cell-2"></div>
    <div class="cell-3"></div>
    <div class="cell-4"></div>
</div>
<div class="third">
    <div class="header">Third</div>
    <div class="cell-1"></div>
    <div class="cell-2"></div>
    <div class="cell-3"></div>
    <div class="cell-4"></div>
</div>

我正在尝试使用 CodeDeploy 将一个简单的 golang Web 服务器部署到 EC2。部署失败并出现以下错误{\"error_code\":6,\"script_name\":\"scripts/start.sh\",\"message\":\"Script at specified location: scripts/start.sh failed to close STDOUT\"。CodeDeploy相关文件：

应用程序规范.yml

version: 0.0

os: linux

files:
  - source: /main.go
    destination: /app/
  - source: /index.html
    destination: /app/
  - source: /config.json
    destination: /app/
  - source: /webserver.log
    destination: /app/

hooks:
  BeforeInstall:
    - location: scripts/cleanup.sh
      timeout: 180
      runas: root
  AfterInstall:
    - location: scripts/build.sh
      timeout: 180
      runas: root
  ApplicationStart:
    - location: scripts/start.sh
      timeout: 180
      runas: root

脚本/cleanup.sh

sudo rm /app -rf
sudo mkdir /app
sudo chown -R ec2-user:ec2-user …