Java--获取环境变量(System.getenv)--方法/实例

短命女 2023-09-29 15:44 15阅读 0赞

原文网址：[Java--获取环境变量(System.getenv)--方法/实例\_IT利刃出鞘的博客-CSDN博客][Java--_System.getenv_--_IT_-CSDN]

## 简介 ##

**说明**

本文用示例介绍Java获得环境变量的方法：System.getenv。

**System.getenv与System.getProperty的区别**

<table> 
 <tbody> 
 <tr> 
 <td>项</td> 
 <td>属性（System.getProperty）</td> 
 <td>环境变量（System.getenv）</td> 
 </tr> 
 <tr> 
 <td>运行时是否可修改</td> 
 <td>可以</td> 
 <td>不可以</td> 
 </tr> 
 <tr> 
 <td>有效范围</td> 
 <td>仅在java平台中有效</td> 
 <td>系统里所有程序都有效</td> 
 </tr> 
 <tr> 
 <td>创建的时机</td> 
 <td>打包应用时属性必须存在</td> 
 <td>可以在任何时候创建环境变量</td> 
 </tr> 
 </tbody> 
</table>

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## **常用方法** ##

<table> 
 <tbody> 
 <tr> 
 <td>方法</td> 
 <td>作用</td> 
 </tr> 
 <tr> 
 <td>System.getenv()</td> 
 <td>获得所有环境变量</td> 
 </tr> 
 <tr> 
 <td>System.getenv(String name)</td> 
 <td>获得名为name的属性的值。</td> 
 </tr> 
 </tbody> 
</table>

## **获得自定义的环境变量** ##

现在指定JAVA\_HOME环境变量，值为JDK路径，如下图所示：

![watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBASVTliKnliIPlh7rpnpg_size_20_color_FFFFFF_t_70_g_se_x_16][]

package com.example.a;
    
    public class Demo {
        public static void main(String[] args) {
            String javaHome = System.getenv("JAVA_HOME");
            System.out.println("javaHome的值:" + javaHome);
        }
    }

执行结果（直接执行或者打成jar包来执行都可以）

![watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBASVTliKnliIPlh7rpnpg_size_15_color_FFFFFF_t_70_g_se_x_16][]

## 打印所有的环境变量 ##

package com.example.a;
 
 import java.util.Map;
 
 public class Demo {
 public static void main(String[] args) {
 Map<String, String> envMap = System.getenv();
 for (Map.Entry<String, String> entry : envMap.entrySet()) {
 System.out.println(entry.getKey() + ":" + entry.getValue());
 }
 }
 }

执行结果：

USERDOMAIN_ROAMINGPROFILE:DESKTOP-QI6B9ME
    NVM_SYMLINK:D:\Program Files\dev\nvm\symlink
    PROCESSOR_LEVEL:23
    SESSIONNAME:Console
    ALLUSERSPROFILE:C:\ProgramData
    PROCESSOR_ARCHITECTURE:AMD64
    PSModulePath:C:\Program Files\WindowsPowerShell\Modules;C:\WINDOWS\system32\WindowsPowerShell\v1.0\Modules
    SystemDrive:C:
    MAVEN_HOME:E:\work\maven\apache-maven-3.6.3
    MOZ_PLUGIN_PATH:D:\Program Files (x86)\Foxit Software\Foxit Reader\plugins\
    USERNAME:knife
    ProgramFiles(x86):C:\Program Files (x86)
    FPS_BROWSER_USER_PROFILE_STRING:Default
    PATHEXT:.COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH;.MSC
    DriverData:C:\Windows\System32\Drivers\DriverData
    ProgramData:C:\ProgramData
    ProgramW6432:C:\Program Files
    HOMEPATH:\Users\knife
    PROCESSOR_IDENTIFIER:AMD64 Family 23 Model 96 Stepping 1, AuthenticAMD
    HADOOP_HOME:D:\dev\bigdata\hadoop-3.2.2
    M2_HOME:E:\work\maven\apache-maven-3.6.3
    ProgramFiles:C:\Program Files
    PUBLIC:C:\Users\Public
    windir:C:\WINDOWS
    =:::::\
    LOCALAPPDATA:C:\Users\knife\AppData\Local
    USERDOMAIN:DESKTOP-QI6B9ME
    FPS_BROWSER_APP_PROFILE_STRING:Internet Explorer
    LOGONSERVER:\\DESKTOP-QI6B9ME
    JAVA_HOME:D:\dev\Java\jdk1.8.0_201
    WebStorm:D:\Program Files\JetBrains\WebStorm 2021.1.3\bin;
    OneDrive:C:\Users\knife\OneDrive
    APPDATA:C:\Users\knife\AppData\Roaming
    CommonProgramFiles:C:\Program Files\Common Files
    Path:C:\Program Files (x86)\Common Files\Oracle\Java\javapath;C:\WINDOWS\system32;C:\WINDOWS;C:\WINDOWS\System32\Wbem;C:\WINDOWS\System32\WindowsPowerShell\v1.0\;C:\WINDOWS\System32\OpenSSH\;d:\Program Files\Git\cmd;D:\dev\Java\jdk1.8.0_201\bin;E:\work\maven\apache-maven-3.6.3\bin;D:\Program Files\mysql-8.0.21-winx64\bin;E:\work\npm\node_global;D:\dev\nodejs\;D:\dev\bigdata\hadoop-3.2.2\bin;D:\dev\bigdata\scala-2.12-13\bin;C:\Users\knife\AppData\Local\Microsoft\WindowsApps;D:\Program Files\JetBrains\WebStorm 2021.1.3\bin;;D:\Program Files\dev\nvm\symlink;C:\Users\knife\AppData\Roaming\npm;
    OS:Windows_NT
    COMPUTERNAME:DESKTOP-QI6B9ME
    PROCESSOR_REVISION:6001
    CommonProgramW6432:C:\Program Files\Common Files
    ComSpec:C:\WINDOWS\system32\cmd.exe
    WXDRIVE_START_ARGS:--wxdrive-setting=0 --disable-gpu --disable-software-rasterizer --enable-features=NetworkServiceInProcess
    SystemRoot:C:\WINDOWS
    TEMP:C:\Users\knife\AppData\Local\Temp
    HOMEDRIVE:C:
    USERPROFILE:C:\Users\knife
    TMP:C:\Users\knife\AppData\Local\Temp
    CommonProgramFiles(x86):C:\Program Files (x86)\Common Files
    NUMBER_OF_PROCESSORS:12
    IDEA_INITIAL_DIRECTORY:C:\Users\knife\Desktop

## 默认环境变量及其含义 ##

<table> 
 <tbody> 
 <tr> 
 <td> 环境变量 </td> 
 <td> 含义 </td> 
 </tr> 
 <tr> 
 <td> USERPROFILE </td> 
 <td> 用户目录 </td> 
 </tr> 
 <tr> 
 <td> USERDNSDOMAIN </td> 
 <td> 用户域 </td> 
 </tr> 
 <tr> 
 <td> PATHEXT </td> 
 <td> 可执行后缀 </td> 
 </tr> 
 <tr> 
 <td> JAVA_HOME </td> 
 <td> Java安装目录 </td> 
 </tr> 
 <tr> 
 <td> TEMP </td> 
 <td> 用户临时文件目录 </td> 
 </tr> 
 <tr> 
 <td> SystemDrive </td> 
 <td> 系统盘符 </td> 
 </tr> 
 <tr> 
 <td> ProgramFiles </td> 
 <td> 默认程序目录 </td> 
 </tr> 
 <tr> 
 <td> USERDOMAIN </td> 
 <td> 帐户的域的名称 </td> 
 </tr> 
 <tr> 
 <td> ALLUSERSPROFILE </td> 
 <td> 用户公共目录 </td> 
 </tr> 
 <tr> 
 <td> SESSIONNAME </td> 
 <td> Session名称 </td> 
 </tr> 
 <tr> 
 <td> TMP </td> 
 <td> 临时目录 </td> 
 </tr> 
 <tr> 
 <td> Path </td> 
 <td> path环境变量 </td> 
 </tr> 
 <tr> 
 <td> CLASSPATH </td> 
 <td> classpath环境变量 </td> 
 </tr> 
 <tr> 
 <td> PROCESSOR_ARCHITECTURE </td> 
 <td> 处理器体系结构 </td> 
 </tr> 
 <tr> 
 <td> OS </td> 
 <td> 操作系统类型 </td> 
 </tr> 
 <tr> 
 <td> PROCESSOR_LEVEL </td> 
 <td> 处理级别 </td> 
 </tr> 
 <tr> 
 <td> COMPUTERNAME </td> 
 <td> 计算机名 </td> 
 </tr> 
 <tr> 
 <td> Windir </td> 
 <td> 系统安装目录 </td> 
 </tr> 
 <tr> 
 <td> SystemRoot </td> 
 <td> 系统启动目录 </td> 
 </tr> 
 <tr> 
 <td> USERNAME </td> 
 <td> 用户名 </td> 
 </tr> 
 <tr> 
 <td> ComSpec </td> 
 <td> 命令行解释器可执行程序的准确路径 </td> 
 </tr> 
 <tr> 
 <td> APPDATA </td> 
 <td> 应用程序数据目录 </td> 
 </tr> 
 </tbody> 
</table>

[Java--_System.getenv_--_IT_-CSDN]: https://knife.blog.csdn.net/article/details/124937020
[Link 1]: https://app.yinxiang.com/fx/d2ac6ff4-94c5-4e5f-9d4f-f5dfc344ede6
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