How to get the value of Environment variables?
The System class in Java provides a method named System.getenv() which can be used to get the value of an environment variable set in the current system.
Syntax:
public static String getenv(String key); where key is the Environment variable whose values we want
Below example illustrates how to use System.getenv() to get the System environment variable:
Example 1: To get the value of a specific environment variable
// Java program to get the value// of a specific environment variable// using System.getenv() method public class GFG { public static void main(String[] args) { // Get the value of // the TEMP environment variable System.out.println(System.getenv("TEMP")); // Get the value of // the OS environment variable System.out.println(System.getenv("OS")); // Get the value of // the JAVA_HOME environment variable System.out.println(System.getenv("JAVA_HOME")); }} |
Output:
Example 2: To get the value of all environment variables at once
// Java program to get the value// of all environment variables at once// using System.getenv() method import java.util.Map; public class GFG { public static void main(String[] args) { // Get the value of // all environment variables at once // and store it in Map Map<String, String> env = System.getenv(); for (String envName : env.keySet()) { System.out.format("%s=%s%n", envName, env.get(envName)); } }} |
Output:
Note: The output will depend on the system on which you run the above code. A sample output is given above
How to get the value of System Property?
The System class in Java has two methods used to read system properties:
- java.lang.System.getProperty(String key): fetches only those properties – values that you will specify using the key(associated to that particular value that you want).
Example:
// Java Program illustrating the working// of getProperty(String key) methodimportjava.lang.*;importjava.util.Properties;publicclassNewClass {publicstaticvoidmain(String[] args){// Printing Name of the system propertySystem.out.println("user.dir: "+ System.getProperty("user.dir"));// Fetches the property set with 'home' keySystem.out.println("home: "+ System.getProperty("home"));// Resulting in Null as no property is present// Printing 'name of Operating System'System.out.println("os.name: "+ System.getProperty("os.name"));// Printing 'JAVA Runtime version'System.out.println("version: "+ System.getProperty("java.runtime.version"));// Printing 'name' propertySystem.out.println("name: "+ System.getProperty("name"));// Resulting in Null as no property is present}}Output:
user.dir: /tmp/hsperfdata_bot home: null os.name: Linux version: 1.8.0_101-b13 name: null
- java.lang.System.getProperty(String key, String definition): helps you to create your own key-value sets that you want.
Example:
// Java Program illustrating the working of// getProperty(String key, String definition) methodimportjava.lang.*;importjava.util.Properties;publicclassNewClass {publicstaticvoidmain(String[] args){// Here key = "Hello" and// System Property = "Geeks"System.out.println("Hello property : "+ System.getProperty("Hello","Geeks"));// Here key = "Geek" and// System Property = "For Geeks"System.out.println("System-property :"+ System.getProperty("System","For Geeks"));// Here key = "Property" and// System Property = nullSystem.out.println("Property-property :"+ System.getProperty("Property"));}}Output:
Hello key property : Geeks System key property :For Geeks Property key property :null
- java.lang.System.getProperties(): fetches all the properties – values that the JVM on your System gets from the Operating System.
Example:
// Java Program illustrating the working of// getProperties() methodpublicclassGFG {publicstaticvoidmain(String[] args){System.out.println(System.getProperties())}}Output:
