Java--获取环境变量(System.getenv)--方法/

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

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常用方法

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：

1.  
   package com.example.a;
2.  
    
3.  
   public class Demo {
4.  
   public static void main(String[] args) {
5.  
   String javaHome = System.getenv("JAVA_HOME");
6.  
   System.out.println("javaHome的值:" javaHome);
7.  
   }
8.  
   }

执行结果（直接执行或者打成jar包来执行都可以）

打印所有的环境变量

1.  
   package com.example.a;
2.  
    
3.  
   import java.util.Map;
4.  
    
5.  
   public class Demo {
6.  
   public static void main(String[] args) {
7.  
   Map<String, String> envMap = System.getenv();
8.  
   for (Map.Entry<String, String> entry : envMap.entrySet()) {
9.  
   System.out.println(entry.getKey() ":" entry.getValue());
10.  
    }
11.  
    }
12.  
    }

执行结果：

1.  
   USERDOMAIN_ROAMINGPROFILE:DESKTOP-QI6B9ME
2.  
   NVM_SYMLINK:D:\Program Files\dev\nvm\symlink
3.  
   PROCESSOR_LEVEL:23
4.  
   SESSIONNAME:Console
5.  
   ALLUSERSPROFILE:C:\ProgramData
6.  
   PROCESSOR_ARCHITECTURE:AMD64
7.  
   PSModulePath:C:\Program Files\WindowsPowerShell\Modules;C:\WINDOWS\system32\WindowsPowerShell\v1.0\Modules
8.  
   SystemDrive:C:
9.  
   MAVEN_HOME:E:\work\maven\apache-maven-3.6.3
10.  
    MOZ_PLUGIN_PATH:D:\Program Files (x86)\Foxit Software\Foxit Reader\plugins\
11.  
    USERNAME:knife
12.  
    ProgramFiles(x86):C:\Program Files (x86)
13.  
    FPS_BROWSER_USER_PROFILE_STRING:Default
14.  
    PATHEXT:.COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH;.MSC
15.  
    DriverData:C:\Windows\System32\Drivers\DriverData
16.  
    ProgramData:C:\ProgramData
17.  
    ProgramW6432:C:\Program Files
18.  
    HOMEPATH:\Users\knife
19.  
    PROCESSOR_IDENTIFIER:AMD64 Family 23 Model 96 Stepping 1, AuthenticAMD
20.  
    HADOOP_HOME:D:\dev\bigdata\hadoop-3.2.2
21.  
    M2_HOME:E:\work\maven\apache-maven-3.6.3
22.  
    ProgramFiles:C:\Program Files
23.  
    PUBLIC:C:\Users\Public
24.  
    windir:C:\WINDOWS
25.  
    =:::::\
26.  
    LOCALAPPDATA:C:\Users\knife\AppData\Local
27.  
    USERDOMAIN:DESKTOP-QI6B9ME
28.  
    FPS_BROWSER_APP_PROFILE_STRING:Internet Explorer
29.  
    LOGONSERVER:\\DESKTOP-QI6B9ME
30.  
    JAVA_HOME:D:\dev\Java\jdk1.8.0_201
31.  
    WebStorm:D:\Program Files\JetBrains\WebStorm 2021.1.3\bin;
32.  
    OneDrive:C:\Users\knife\OneDrive
33.  
    APPDATA:C:\Users\knife\AppData\Roaming
34.  
    CommonProgramFiles:C:\Program Files\Common Files
35.  
    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;
36.  
    OS:Windows_NT
37.  
    COMPUTERNAME:DESKTOP-QI6B9ME
38.  
    PROCESSOR_REVISION:6001
39.  
    CommonProgramW6432:C:\Program Files\Common Files
40.  
    ComSpec:C:\WINDOWS\system32\cmd.exe
41.  
    WXDRIVE_START_ARGS:--wxdrive-setting=0 --disable-gpu --disable-software-rasterizer --enable-features=NetworkServiceInProcess
42.  
    SystemRoot:C:\WINDOWS
43.  
    TEMP:C:\Users\knife\AppData\Local\Temp
44.  
    HOMEDRIVE:C:
45.  
    USERPROFILE:C:\Users\knife
46.  
    TMP:C:\Users\knife\AppData\Local\Temp
47.  
    CommonProgramFiles(x86):C:\Program Files (x86)\Common Files
48.  
    NUMBER_OF_PROCESSORS:12
49.  
    IDEA_INITIAL_DIRECTORY:C:\Users\knife\Desktop

默认环境变量及其含义

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