What's New in J/Link 2

Changes in version 2.0.1

Fixes a bug that can cause the Java runtime to shut down in some circumstances on Java 1.1.x version runtimes (e.g., Mac OS 8/9, or Windows users using the Microsoft Java runtime).

Improves behavior of the Mathematica front end on Windows when it is launched to provide graphics rendering services for Java programs.

Fixes minor classpath problems on Mac OS 8/9.

Improves color scheme used by the ConsoleWindow class.

Changes in version 2.0.0

Special Notes:

The location of JLink.jar within the JLink directory structure was changed in this release. Users of previous versions with CLASSPATH specifications that point at JLink.jar will need to revise them. JLink.jar is now in the JLink directory itself, not JLink/SystemAdditions.

A number of functions have been renamed. The old names are deprecated, meaning that they still work but might be removed in the future. All new code should use the new names. Here are the old and new names:

old name	new name
LoadClass	LoadJavaClass
ReleaseObject	ReleaseJavaObject
Val	JavaObjectToExpression
ByRef	ReturnAsJavaObject
GetClassPath	JavaClassPath

Version 2.0 is a significant upgrade with many new features and improvements. Here are the most important ones:

Mac OS X is supported.

Dramatic speed improvements have been made for calling Java methods. This makes the MethodFunction and FieldFunction optimizations more or less obsolete.

One of the most difficult parts of J/Link installation was putting the native library in the correct location. This is no longer necessary. The native library should remain where it is, buried deep in the JLink directory structure.

The way in which Java is launched by InstallJava is new. One consequence of this is that the ClassPath option works differently. The default setting, Automatic, means that the value of the CLASSPATH environment variable will be used. However, if you set a value for ClassPath, that value is used instead of the CLASSPATH environment variable.

There is a new component called com.wolfram.jlink.ui.MathSessionPane that implements a complete In/Out session window, similar to the kernel's raw "terminal" interface, but with many more features, including: graphics support, syntax coloring of input, bracket matching, copy input from above, customizable colors and fonts, full text editing features within the current input "cell" including cut/copy/paste/undo/redo, and more.

A new component called MathGraphicsJPanel is the Swing counterpart to the existing AWT-based MathCanvas. Use this component to easily display Mathematica graphics and typeset expressions in your programs.

There is a new Mathematica function, ShowJavaConsole[], that displays a window showing Java console output (i.e., theSystem.out and System.err streams). On Windows, you no longer see a DOS Java console window appear when Java launches.

The JavaBlock function is improved to give it more control over what objects are released when it ends. These improvements make some common programming idioms easier, without having to resort to manual use of ReleaseObject. If you return a Java object as the sole result of a JavaBlock, that object is not released. There is also a new KeepObjects option to JavaBlock that allows you to specify a list of one or more objects that will not be released at the end.

The new ImplementJavaInterface function lets you implement any Java interface entirely with Mathematica code. Among other uses, this means that you can create any "listener"-type object in Mathematica without requiring a Java MathXXXHandler class to already exist for that interface.

There is a SetInternetProxy function that allows users to specify proxy port and host information, if such settings are necessary to reach the internet.

There is a new MakeJavaExpr[] function that lets you construct, from Mathematica, a Java Expr object from an arbitrary Mathematica expression.

The AddToClassPath function was added to supersede the functionality provided by $ExtraClassPath.

There is a new JLink`Information` context that defines symbols giving version information. The symbols are $Version, $VersionNumber, $ReleaseNumber.

Working with periodical tasks is now more flexible with the new function SetPeriodicalInterval and the new variable $ThisPeriodical.

For Java programmers, the MLGetType, MLGetNext methods when applied to a KernelLink object can now return KernelLink.MLTKOBJECT in addition to MLTKSTR, MLTKINT, etc. MLTKOBJECT means that the expression on the link is a Java object reference and can be read with getObject().

The MathLink connect() method now includes an optional timeout parameter giving the number of milliseconds to wait for the connection before throwing an exception.

The MathLink interface now has a second signature for the getArray method: getArray(int type, int depth, String[] heads). This method reads an array and tells you what the heads were at each level.

A getLastError() method was added to the KernelLink interface. If one of the evaluateTo methods returns null, you can call getLastError() to get the Throwable object that caused the problem.

The methods interruptEvaluation(), abortEvaluation(), abandonEvaluation(), and terminateKernel() were added to the KernelLink interface. These methods free the programmer from having to deal directly with low-level MathLink messages.

The Expr class has been extended and made faster and more robust.