FrontEndSharedQ[link] returns True if the front end is being shared with a specified link, and returns False otherwise.

GetJavaException[] returns the Java Exception object that was thrown in the most recent call from Mathematica to Java.

MakeJavaExpr[expr] constructs a new Java object of the J/Link Expr class that represents the Mathematica expression expr.

Periodical[id] returns information about the periodical task corresponding to the specified integer id.

Periodicals[] returns a list of integer ID numbers corresponding to the set of operations that are periodically performed automatically when the kernel is not busy with ...

ReinstallJava[] is a convenience function that calls UninstallJava followed by InstallJava.

SetField[obj@field, val] sets a value of an object field.

UseFrontEnd[expr] evaluates expr in an environment where the kernel can make use of the services of the notebook front end.

$FrontEndInitializationFunction is a function that you can assign to execute when the front end link is first established by ConnectToFrontEnd[].