How do I programmatically determine operating system in Java?

Question

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 propertie

Answer 1

If you're working in a security sensitive environment, then please read this through.

Please refrain from ever trusting a property obtained via the System#getProperty(String) subroutine! Actually, almost every property including os.arch, os.name, and os.version isn't readonly as you'd might expect — instead, they're actually quite the opposite.

First of all, any code with sufficient permission of invoking the System#setProperty(String, String) subroutine can modify the returned literal at will. However, that's not necessarily the primary issue here, as it can be resolved through the use of a so called SecurityManager, as described in greater detail over here.

The actual issue is that any user is able to edit these properties when running the JAR in question (through -Dos.name=, -Dos.arch=, etc.). This means that there's no way to determine if these properties are indeed actually accurate. Because of this, here are a few additional checks to try and avoid tampering:

// The first thing we're able to do is to query the filesystem.
switch (java.io.File.separator)
{
    case "/":
        // Windows is a potential candidate.
        break;
    case "\\":
        // And here it could really be anything else.
        break;
    default:
        // There's probably something really wrong here by now.
        break;
}