1. System.getenv(String variable) that returns specific environment variable value
2. System.getenv() that returns all environment variables values
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What are environment variables?
Environment variables are key/value pairs just like properties in the Java platform where both the key and the value are strings.A few Operating Systems use environment variables to transfer configuration information to applications.
Java Program to get the specific environment variable
System.getenv(String name) - We will use System.getenv(String name) to get the specified environment variable. In the below java program, we are getting the value of the "JAVA_HOME" environment variable. public class GetEnvironmentVariable {
public static void main(String args[]) {
System.out.println("Get Specific Environment Variable");
System.out.println("JAVA_HOME value is: " + System.getenv("JAVA_HOME"));
}
}Output:
Get Specific Environment Variable
JAVA_HOME value is: C:\Program Files\Java\jdk1.8.0_291
Java Program to get all environment variables
System.getenv() - This method returns all environment variables. Since environment variables are string key/value pairs. This method will return all the environment variables as a map of variable names to values(Map<String,String>). import java.util.Map;
public class GetEnvironmentVariable2 {
public static void main(String args[]) {
System.out.println("Get All Environment Variables");
Map<String,String> mapObj = System.getenv();
for (Map.Entry<String,String> entry : mapObj.entrySet()) {
System.out.println("Key: " + entry.getKey()+ " Value: "+ entry.getValue());
}
}
}Output:
Get All Environment Variables
Key: MyOffice Value: BLR
Key: PROCESSOR_LEVEL Value: 6
Key: SESSIONNAME Value: Console
Key: ALLUSERSPROFILE Value: C:\ProgramData
Key: PROCESSOR_ARCHITECTURE Value: AMD64
Key: PSModulePath Value: C:\Program Files\WindowsPowerShell\Modules;C:\WINDOWS\system32\WindowsPowerShell\v1.0\Modules;C:\Program Files (x86)\Microsoft Azure Information Protection\Powershell
Key: SystemDrive Value: C:
Key: USERNAME Value: submittal
Key: ProgramFiles(x86) Value: C:\Program Files (x86)
Key: FPS_BROWSER_USER_PROFILE_STRING Value: Default
Key: PATHEXT Value: .COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH;.MSC;.PY;.PYW
Key: DriverData Value: C:\Windows\System32\Drivers\DriverData
Key: ProgramData Value: C:\ProgramData
Key: ProgramW6432 Value: C:\Program Files
Key: HOMEPATH Value: \Users\SUBMITTAL
Key: MyScriptVer Value: DomainLogonVista.vbs-2a
Key: PROCESSOR_IDENTIFIER Value: Intel64 Family 6 Model 142 Stepping 12, GenuineIntel
Key: ProgramFiles Value: C:\Program Files
Key: PUBLIC Value: C:\Users\Public
Key: windir Value: C:\WINDOWS
Key: =:: Value: ::\
Key: LOCALAPPDATA Value: C:\Users\SUBMITTAL\AppData\Local
Key: ChocolateyLastPathUpdate Value: 132690986583143576
Key: USERDOMAIN Value: US
Key: FPS_BROWSER_APP_PROFILE_STRING Value: Internet Explorer
Key: JAVA_HOME Value: C:\Program Files\Java\jdk1.8.0_291
Key: OneDrive Value: C:\Users\Administrator\OneDrive
Key: APPDATA Value: C:\Users\SUBMITTAL\AppData\Roaming
Key: ChocolateyInstall Value: C:\ProgramData\chocolatey
Key: MyFunction Value: CG
Key: CommonProgramFiles Value: C:\Program Files\Common Files
Key: Path Value: C:/Users/SUBMITTAL/Downloads/eclipse-jee-2021-06/eclipse//plugins/org.eclipse.justj.openjdk.hotspot.jre.full.win32.x86_64_16.0.1.v20210528-1205/jre/bin;C:\Python39\Scripts\;C:\Python39\;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\;C:\Users\SUBMITTAL\AppData\Local\Microsoft\WindowsApps;C:\Program Files\Git\cmd;C:\Program Files\nodejs\;C:\ProgramData\chocolatey\bin;C:\Users\SUBMITTAL\AppData\Local\Microsoft\WindowsApps;C:\Users\SUBMITTAL\AppData\Roaming\npm;C:\Users\SUBMITTAL\Downloads\eclipse-jee-2021-06\eclipse;
Key: NEXTHINK Value: C:\Program Files\Nexthink\Collector
Key: OS Value: Windows_NT
Key: CommonProgramW6432 Value: C:\Program Files\Common Files
Key: ComSpec Value: C:\WINDOWS\system32\cmd.exe
Key: SystemRoot Value: C:\WINDOWS
Key: TEMP Value: C:\Users\SUBMIT~1\AppData\Local\Temp
Key: HOMEDRIVE Value: C:
Key: USERPROFILE Value: C:\Users\SUBMITTAL
Key: TMP Value: C:\Users\SUBMIT~1\AppData\Local\Temp
Key: CommonProgramFiles(x86) Value: C:\Program Files (x86)\Common Files
Key: NUMBER_OF_PROCESSORS Value: 8
That's all for today. Please mention in the comments in case you have any other questions related to getting the environment variables in Java.
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