How to compile Java program with .jar library

Question

I can't make javac recognize an external .jar file, whose classes I'm trying to extend. I have two files in the same directory: TestConsole.java and acm.jar. I'm compiling from the same directory using the following command:

javac -classpath .:acm.jar TestConsole.java

But it seems like javac is just ignoring acm.jar. It gives me the error:

TestConsole.java:1: package acm does not exist
import acm.program;
          ^

Of course, acm.program is a package in acm.jar. All of the classes in acm.jar are already compiled; I just want to use them in my classes, not compile them.

What am I doing wrong?

I am running this on a Mac, and the directory structure of acm.jar appears to be valid: It contains an acm/program directory, which has ConsoleProgram.class, the only class that TestConsole extends.

javac -classpath ".:acm.jar" TestConsole.java does not work, either.

Answer 1

javac -cp <jar you want to include>;<jar you want to include> <source.java> 

<jar you want to include> if in same directory, just name of jar will do, if not, specify full or relative paths

if more than one jars, separate with ,

replace ; with : on unix

If possible, use some IDE like Eclipse. I used to spend a lot of time on similar things, but in industry, you will hardly ever do it in this fashion.

Answer 2

Are you running these commands on a Windows machine? On Windows, the elements of the classpath are separated by a semicolon, not a colon. So:

javac -classpath .;acm.jar TestConsole.java

Another possibility: the structure of acm.jar is wrong. It's not sufficient that the class files inside were compiled from files that declare package acm.program - the package structure must also be represented as a directory hierarchy, so acm.jar must contain a directory acm, and within that a subdirectory program that contains the actual class files for the classes used in TestConsole.