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Mac OS X Java System Properties

This appendix lists the Mac OS X–specific system properties that you should be aware of.

Java Virtual Machine Properties

You can use System.getProperties().list(System.out) to obtain a complete list of system properties. The most useful ones are included here, as well as brief descriptions.

The properties in Table C-1 all return a value of type String. They can be used in this manner:

if (System.getProperty("os.version").equals("10.2"))

 System.out.println("Mac OS X version 10.2 Jaguar");

**Table C-1** JVM properties
Property	Value	Notes
`java.version`	1.3.1
`java.vm.version`	1.3.1_03-69
`line.separator`	‘\n’	This differs from MRJ in Mac OS 9, which used `\r`, but is consistent with UNIX-based Java implementations and with the BSD and Cocoa frameworks.
`mrj.version`	3.3	Testing for the existence of this property is the general way to detect whether you are using an Apple-developed JVM. To detect specific features like JDirect or MRJToolkit, it is better to use reflection to check for the existence of the specific classes they use.
`os.name`	Mac OS X	This value was `Darwin` in developmental versions of Mac OS X. The MRJ on Mac OS 9 used `Mac OS`. It is suggested that you use `System.getProperty("os.name").startsWith("Mac OS")` if you need to test whether your code is running on any version of Mac OS.
`os.version`	10.2	This is the version number available in the About This Mac dialog. Developmental versions of Java on Mac OS X used the Darwin kernel number (1.1, 1.2, and so forth)

Mac OS X Application Properties

It is simple to wrap your pure Java application inside of a natively executable Mac OS X application bundle. This is discussed in Mac OS X Java Applications. In so doing, there are two properties that must be defined. These are listed in Table C-2. If you are using Project Builder or MRJAppBuilder, you do not need to do anything to define them since both of those applications take care of this for you.

**Table C-2** required Mac OS X application properties
Property	`Info.plist` key	Description
`com.apple.mrj.application.main`	`MainClass`	The fully qualified class name of the class containing the application’s `main` method.
`com.apple.mrj.application.classpath`	`ClassPath`	The paths of all required directories or JAR files.

In addition, you can pass in the options listed in Table C-3.

**Table C-3** Application launch properties
Property	Info.plist Key	Description
`com.apple.mrj.application.parameters`	`Arguments`	Space-separated list of arguments that are parsed to build the `String[]` passed to `main`.
`com.apple.mrj.application.workingdirectory`	`WorkingDirectory`	Sets the current working directory for the application. By default the current working directory is set to the parent directory of the application bundle. The `APP_PACKAGE` variable may be used to refer to the root of the application bundle.
`com.apple.mrj.application.vm.options`	`VMOptions`	Space-separated list of options for the Java virtual machine. These are the `-X` and `-XX` options without the `-X(X)` prefix.

Note the following about these properties:

None of these properties are set by default.
If you are adding properties to an Info.plist, they should go into the Java dictionary.
When adding properties to an Info.plist, do not use the fully qualified package name. Instead use the Info.plist key value designated in the appropriate table.
In setting the values for any of these keys, you may take advantage of two variables unique to application bundles:

APP_PACKAGE
The root directory of the application bundle.
JAVAROOT
This is not set by default. If you do set it in the Info.plist file, you may use $JAVAROOT to resolve its value.
Note: These variables are used only by Mac OS X for launching your application. Do not use them in your Java code.

Mac OS X–Specific Properties

The properties listed in Table C-4 are all properties that are found only on Mac OS X. Overall they help your applications to fit in more cleanly with the rest of the Mac OS X environment. They can be set three ways:

In the Info.plist or MRJApp.properties files through Project Builder or MRJAppBuilder respectively. You can modify these files later with a text editor.
In your main class as arguments to System.setProperty.
From the command-line using the -D flag as follows:
java -Dcom.apple.macosx.useScreenMenuBar=trueYourSwingApp

**Table C-4** System properties related to the graphical user interface
Property	Default Value	Notes
`com.apple.hwaccel`	`true`	Turns on hardware graphics acceleration for the video cards not commented out of `/Library/Java/Home/lib/hwexclude.properties.`If set to `false`, hardware acceleration is turned off. It may be used in conjunction with the `com.apple.hwaccelexclude` property.
`com.apple.hwexclude`	`none`	When specific video card designation strings are passed in with this property, hardware graphics acceleration is not turned on for the respective video cards. It is be on for all other video cards. When this property is set, `/Library/Java/Home/lib/hwexclude.properties` is ignored.
`com.apple.macos.use-file-dialog-packages`	`false`	When set to `true`, causes `java.awt.FileDialog` to show application packages as if they were files and does not allow navigation into them.
`com.apple.macos.useScreenMenuBar`	`false`	Puts Swing menus in the Mac OS X menu bar if using the Aqua look and feel. Java applications created with Project Builder have this set to `true`. Note that JMenuBars in JDialogs are not moved to the Mac OS X menu bar.
`com.apple.macos.useSmallTabs`	`none`	If defined, and set to `true`, tab controls in Swing applications more closely resemble the Metal look and feel. If set to `false`, the tabs assume a larger size more similar to the default Aqua controls.
`com.apple.macosx.AntiAliasedTextOn`	`true`	Use anti-aliasing when rendering text.
`com.apple.macosx.AntiAliasedGraphicsOn`	`true`	Use anti-aliasing when rendering graphics.
`com.apple.mrj.application.apple.menu.about.name`	None	If defined, an About command is added to the top of the application menu and can be detected by registering a `com.apple.mrj.AboutHandler`. Java applications created with Project Builder have this set to initial name of your project.
`com.apple.mrj.application.growbox.intrudes`	`true`	Resizable window’s growbox (resize control) intrudes into AWT content. If turned off, the bottom of the window is pushed down 15 pixels.
`com.apple.mrj.application.live-resize`	`false`	Enables live resizing of windows.

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