I was considering making a program that includes using the javac tool, as well as the java command line tool, in the GUI as a critical part. As an example I would site an IDE like NetBeans, which can compile your files as well as run a "mini" command line in the bottom of the window when you run your program.
How would I go about using javac to compile files in my program, and how would I go about displaying the command line output of the java tool in a textarea in my program? Any leads, however small, would be much appreciated!!!
Java 6 has a new API for using the Java compiler from within a Java program. See the documentation of package javax.tools.
If you're using an older version of Java, then you could call the Java compiler as an external process using Runtime.exec() or class ProcessBuilder, and then catching the output of the stdout / stderr streams.