JExternal is a 4D plug-in to execute Java methods from within 4D. JExternal enables you to use many useful Java libraries 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-in methods. Besides JExternal allows the Java methods to callback 4D methods.
Create a "JavaClasses" folder and put Java files whose extensions are ".jar" into it. Java methods in the Jar files can be executed from within 4D.
Java methods called from within 4D are executed in a 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 another 4D plug-in and distributed with JExternal, in order to launch a Java virtual machine.