Java Command Line Trouble with Reading a Class from a Jar Archive

Question

I am trying to run a java based tool using a command line syntax as the following: java -cp archive.jar archiveFolder.theMainClassName.Although the class I am searching for, a main class, "theMainClassName" is in the archive.jar and in the archiveFolder given at input, I keep getting the error that my class is not seen. Does anybody have any ideas concerning this problem? Thank you in advance

Answer 1

Here's a concrete example of what does work, so you can compare your own situation.

Take this code and put it anywhere, in a file called MainClass.java. (I've assumed a directory called src later. Normally you'd arrange the source to match the package, of course.)

package archiveFolder;

public class MainClass
{
    public static void main(String[] args)
    {
        System.out.println("I'm MainClass");
    }
}

Then run each of these commands:

# Compile the source
javac -d . src/MainClass.java

# Build the jar file
jar cf archive.jar archiveFolder

# Remove the unpackaged binary, to prove it's not being used
rm -rf archiveFolder # Or rmdir /s /q archiveFolder on Windows

# Execute the class
java -cp archive.jar achiveFolder.MainClass

The result:

I'm MainClass

How are you building your jar file? Is the code in the appropriate package?