Monday, May 9, 2011

How to Access System Properties?

This code example shows how to list all system properties, get/set the value of a system property:

import java.util.Enumeration;
import java.util.Properties;
//some logics....
//prints all the system properties onto the console
public static void listAllSystemProperties() {

//List All System Properties
Properties props = System.getProperties();
Enumeration enumeration = props.keys();
while (enumeration.hasMoreElements()) {
String propName = (String) enumeration.nextElement();
String propValue = (String)props.get(propName);
System.out.println(propName + " = " + propValue);

// Set a system property
String previousValue = System.setProperty("myjava.version", "5.0");
//Get a system property
String version = System.getProperty("myjava.version");
System.out.println("myjava.version=" + version);


Here is an example to get the working directory (which is the location in the file system from where the java command was invoked):

    String curDir = System.getProperty("user.dir");

A system property can be set or overridden by specifying the -D option to the java command when running your program.

    java -Dmyjava.version="5.0" MyApplication

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