Question

So I’m pretty sure I looked as well as I could before asking this question, so here goes.
I am writing a Java class for RC4 encryption, I’d like to make use of the Files class in Google Guava. I am compiling using javac on the Ubuntu command line. I am trying to link the jar file, guava-10.0.1.jar” to my class to no success.

This is a snippet from the top:

import java.util.*;
import java.io.*;
import com.google.common.io.*;

class rc4 {

 private static int S[] = new int[256];
 private static int kLen;

 public static void main(String[] args) {
 ...

The line specific to what I am calling is as follows, fully in a try block:

 byte plain[] = Files.toByteArray(file);

I then compile using this:

$ javac -cp FULL/FILE/PATH/guava-10.0.1.jar rc4.java

It compiles, but when I try to run java rc4 with the options I defined to access the function, I get the error:

Exception in thread "main" java.lang.NoClassDefFoundError: com/google/common/io/Files
        at rc4.main(rc4.java:58)
Caused by: java.lang.ClassNotFoundException: com.google.common.io.Files
  at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
  at java.security.AccessController.doPrivileged(Native Method)
  at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
  at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
  at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
  at java.lang.ClassLoader.loadClass(ClassLoader.java:248)
   ... 1 more

I’ve tried a few different calls, and have checked the jar to make sure its not a jar, in a jar, in a jar etc. I then tried using a manifest file:

Manifest-Version: 1.0
Created-By: me
Main-Class: rc4
Class-path: /FULL/FILE/PATH/guava-10.0.1.jar

And then create a jar as such:

jar cvf0m rc4.jar manifest.txt rc4.class

and then run it with:

java -jar rc4.jar

to which I get the same error as above, but it’s saying “rc4” can not be found instead.
So, I’m a little lost to what I’m missing. I am still a lil fresh to Java so if I’m missing some huge obviously basic necessity I sincerely apologize for the oversight, but if anyone can offer me some help in this, I would really appreciate it.

Answer 1

To test that your code actually works you can try manually specifying the classpath:

java -cp yourProject.jar:/path/to/guava-10.0.1.jar rc4

Note that you need to specify both project and lib on the classpath like that or rc4 which is from your project JAR will not be found! (As an aside: consider using packages in your project.)

Then if that works it is time to check your JAR manifest:

1. Is it located in a directory inside the JAR file called META-INF
2. Is it called MANIFEST.MF
3. Does the Class-Path contain your classpath, with proper case and so on? Note your attribute is called Class-path instead.)