How do I programmatically determine operating system in Java?

I would like to determine the operating system of the host that my Java program is running programmatically (for example: I would like to be able to load different properties based on whether I am on a Windows or Unix platform). What is the safest way to do this with 100% reliability?

Solution 1:

You can use:

System.getProperty("os.name")

P.S. You may find this code useful:

class ShowProperties {
    public static void main(String[] args) {
        System.getProperties().list(System.out);
    }
}

All it does is print out all the properties provided by your Java implementations. It'll give you an idea of what you can find out about your Java environment via properties. :-)

Solution 2:

As indicated in other answers, System.getProperty provides the raw data. However, the Apache Commons Lang component provides a wrapper for java.lang.System with handy properties like SystemUtils.IS_OS_WINDOWS, much like the aforementioned Swingx OS util.

Solution 3:

Oct. 2008:

I would recommend to cache it in a static variable:

public static final class OsUtils
{
   private static String OS = null;
   public static String getOsName()
   {
      if(OS == null) { OS = System.getProperty("os.name"); }
      return OS;
   }
   public static boolean isWindows()
   {
      return getOsName().startsWith("Windows");
   }

   public static boolean isUnix() // and so on
}

That way, every time you ask for the Os, you do not fetch the property more than once in the lifetime of your application.

February 2016: 7+ years later:

There is a bug with Windows 10 (which did not exist at the time of the original answer).
See "Java's “os.name” for Windows 10?"