How to compile a single Java file

Question

I have searched this, but I could'n find or understand what I found.
Now I'm not a Java programmer, but I have the need to compile a single Java file into an existing (compiled) Java program. The source of this Java code is not available to me, therefore I cannot compile the entire project.
I'm not interested in decompiling the original project.

How to quickly do this using only the JDK and javac? (Through the command line is what I prefer.)

I understand that to do so error checking outside of the single java file will have to be disabled, because it can't read the dependencies.

Thanks in advance,
-Aidiakapi

EDIT: I do have the JAR file, thanks for the answer :)

amesh · Accepted Answer · 2012-10-19 11:56:47Z

31

As far as I can understand you want to re-compile a single java file and replace it in an existing jar file..

So you compile it..

cmd>javac -classpath jar1.jar;jar2.jar my.company.MyClassToReplace.java

and replace it in the jar.

cmd>jar uf myJarFile.jar my/company/MyClassToReplace.class

edited Oct 19, 2012 at 11:56

amesh

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answered Feb 11, 2011 at 14:47

Oleg Pavliv

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2 Comments

manikanta nvsr Over a year ago

How can I do this for a war? My project takes a lot of time to compile whole project. Is there any way I can recompile a single java file with changes gets added to the already created target folder?

Oleg Pavliv Over a year ago

@manikanta nvsr war is a collection of jars. So you rebuild a jar and then replace it in the war file

Peter Lawrey · Accepted Answer · 2011-02-11 14:35:42Z

20

You need to have the jar(s) which contains all the things your class depends on to compile it.

You can then compile the Class with

javac -classpath jar1:jar2 mypackage.MyNewClass

If you have no access to the original Jars, you will have to create mock classes and method etc (which don't have to do anything, just be there so your class compiles) Using an IDE can make both processes easier. (That is what it is for ;)

answered Feb 11, 2011 at 14:35

Peter Lawrey

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4 Comments

Nathan Hughes Over a year ago

He says he doesn't have the source, but it sounds like he does have the jars. I think he should be ok without mocks.

Aidiakapi Over a year ago

I'm not getting it to work. I have a java file (Client.java), and it's in this subfolder: net/client/Client.java The jar file is in the root directory. It gives errors at the ; behind the imports.

Peter Lawrey Over a year ago

This means the jars it could find, don't have the package you are using. Most likely your list of jars is incorrect. Note: on ms-dos you need to use ; instead of :

Aidiakapi Over a year ago

It is only one jar file, so that shouldn't cause any problem.

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