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Compile at runtime

Mike Broadbear
Ranch Hand

Joined: Jan 14, 2002
Posts: 39
Is there a way to compile a .java source file at runtime?
Michael Morris
Ranch Hand

Joined: Jan 30, 2002
Posts: 3451
Hi Mike,
Yep, checkout java.lang.Runtime. It has all of the old Unix style exec() functions. For example:

Hope this helps,
Michael Morris


Any intelligent fool can make things bigger, more complex, and more violent. It takes a touch of genius - and a lot of courage - to move in the opposite direction. - Ernst F. Schumacher
Dirk Schreckmann
Sheriff

Joined: Dec 10, 2001
Posts: 7023
Deos anybody know if such commands work on Macs?


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Cindy Glass
"The Hood"
Sheriff

Joined: Sep 29, 2000
Posts: 8521
From Apples - The Care and Feeding of Runtime.exec.

For example, you can invoke the Java compiler thusly:
String args = {"java", "sun.tools.javac.Main", ...javac argument list...};
Runtime.getRuntime().exec(args);


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john guthrie
Ranch Hand

Joined: Aug 05, 2002
Posts: 124
You don't need to Runtime.exec the compiler. I know ant doesn't do this...
Looking at the ant source code, it looks like they use a class names "sun.tools.javac.Main", so if you can find that (again, the ant src distro would help here), you can do it
Michael Morris
Ranch Hand

Joined: Jan 30, 2002
Posts: 3451
Hi John,
That is a good point. Most of us tend to forget about the propriatery packages that are available to us since there is usually not a published API nor any guarantee that they will remain as is. But I'm sure your method would work fine.
Michael Morris
Dave Landers
Ranch Hand

Joined: Jul 24, 2002
Posts: 401
Check Rodey Green's Java Glossary entry on javac - under the table of command line switches he gives a usage example.
This class is in JAVA_HOME/lib/tools.jar, so you have to include that in CLASSPATH to use it from a program.
As I recall, the main() method is used from javac.exe, but it does a System.exit() - so you don't want to do that from your program. Use the compile() method which returns a boolean for success/fail.
 
 
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