| Creating an Applet User Interface

## Reading System Properties

> To find out about the current working environment, applets can read system properties. System properties are key/value pairs that contain information such as the operating system that the applet is running under. System properties are covered in detail in the System Properties page.

> Applets can read some, but not all, system properties. This page lists the system properties that Netscape Navigator 2.0 and the Applet Viewer allow applets to read, followed by a list of properties that applets can't read.

> #### System Properties that Applets Can Read

> > Applets can read the following system properties:

> > Key | Meaning
> > `"file.separator"` | File separator (for example, "/")
> > `"java.class.version"` | Java class version number
> > `"java.vendor"` | Java vendor-specific string
> > `"java.vendor.url"` | Java vendor URL
> > `"java.version"` | Java version number
> > `"line.separator"` | Line separator
> > `"os.arch"` | Operating system architecture
> > `"os.name"` | Operating system name
> > `"path.separator"` | Path separator (for example, ":")

> > To read a system property from within an applet, the applet uses the `System` class method `getProperty`. For example:

> > >     String s = System.getProperty("os.name");

> #### Forbidden System Properties

> > For security reasons, no existing browsers or applet viewers let applets read the following system properties.

> > Key | Meaning
> > `"java.class.path"` | Java classpath
> > `"java.home"` | Java installation directory
> > `"user.dir"` | User's current working directory
> > `"user.home"` | User home directory
> > `"user.name"` | User account name

> | Creating an Applet User Interface