JExternal is a plug-in for 4D that enables to execute Java methods from within 4D. A lot of useful libraries written in Java
can be used in 4D.
JExternal looks for Java files in "JavaClasses" folder and allows Java methods in those files to be used
as if they were 4D plug-ins methods. Besides it allows the Java methods to callback 4D methods.
Create a "JavaClasses" folder and put Java files whose extensions are ".jar" into it. Then Java methods in the files can be executed from within 4D.
In JExternal ver 4.1.1 or later, Java methods called from within 4D are executed in a native thread corresponding to a 4D process. If Java methods are called from two processes at the same time, they are executed in parallel.
JExternal requires JWorld which is the plug-in to launch a Java virtual machine for JExternal.