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Language: Java Language
Expertise: Beginner

Mar 19, 1997

Question:
Is there a way to make a binary executable from Java code?

Answer:
There are several stunts you could try in order to accomplish this, but they all cripple the platform independence of your Java programs.

For example, on Unix or Wintel systems, you could create a shell script or batch file that included the relevant class files, extracted them into a temporary directory and then invoked the Java interpreter on the class files with the right arguments. This means you can invoke the program with just one command without having to set a CLASSPATH variable first or to explicitly invoke the Java interpreter on the commandline. In fact, this is how HotJava (itself written in Java) is invoked. But shell scripts are not very cross-platform and introduce bugs and insecurity for the user.

If shell scripts are not an option, you could write a C program that set the appropriate environment variables and then invoked a secondary binary - in this case the Java interpreter - with the right set of parameters. Unix platforms can do this with the system() call, other platforms also have similar system-dependent library routines that allow applications to invoke other programs. The class files can be statically compiled into the binary as arrays of data or can accompany the program as set up files depending on how tightly you wish to bundle the various files.

Both of these stunts of course, assume that you have the Java interpreter available on the system. If that's not the case, then you can pretty much forget having an executable Java program because your Java application will need the Java libraries, class files, and set up info that comprise Java's core packages.

This may become less of an issue in the future since most computer vendors have announced plans to make a Java virtual machine implementation available for their platforms. This would mean that every system will have a Java interpreter or just-in-time compiler built right into the operating system of the machine.