Could not find or load main class with a Jar File

Question

I'm trying to load a jar using

@echo off
java -jar Test.jar
pause

With the manifest of

Manifest-Version: 1.0
Main-Class: classes.TestClass

In the Jar directory, I can clearly see a classes\TestClass file when I extract it.

Edit: classes.TestClass does have a public static void main(String[] args).

Package Deceleration in classes.TestClass is package classes;

But I still keep getting the error message

Could not find or load main class classes.TestClass

I've been through everything I've been able to find with this problem, and none of it seems to help.

I've tried editing the classpath, redoing the manifest, installing the new JRE.

What else should I be doing?

Answer 1

I got it working like this:

TestClass.Java

package classes;

public class TestClass {

    public static void main(String[] args) {
        System.out.println("Test");
    }

}

Use javac on the command line to produce TestClass.class. Put TestClass.class in a folder classes/.

MANIFEST.MF

Manifest-Version: 1.0
Main-Class: classes.TestClass

Then run

jar cfm test.jar MANIFEST.MF classes/

Then run it as

java -jar test.jar

Answer 2

java -cp "full-path-of-your-jar" Main

to run any other class having "public static void main" in some package,

java -cp "full-path-of-your-jar" package1.package2.packages-hierarchy.ClassHavingMain

Answer 3

1.Create a text file calles Manifest.txt and provide the value as

Main-Class: classes.TestClass

2.Create the jar as

jar cfm test.jar Manifest.txt classes/*.class

3.Run the jar as

java -jar test.jar

Answer 4

I just had the same problem in the end its because i copied and pasted the code off word and it was a slightly different type of '-' character used, thats all i can think of, when i typed it in manually it worked

Answer 5

This is very difficult to debug without complete information.

The two most likely-looking things at this point are that either the file in the jar is not stored in a directory WITHIN THE JAR, or that it is not the correct file.

You need to be storing TestClass.class - some people new at this store the source file, TestClass.java.

And you need to create the jar file so that TestClass.class appears with a path of classes. Make sure it is not "/classes". Use zip to look at the file and make sure it has a path of "classes".

Answer 6

I had a similar problem which I could solve by granting execute-privilege for all parent folders in which the jar-file is located (on a linux system).

Example:

/folder1/folder2/folder3/executable.jar

all 3 folders (folder1, folder2 and folder3) as well as the executable.jar need execute-privilege for the current user, otherwise the error "Could not find or load main class ..." is returned.

Answer 7

I had a weird issue when an incorrect entry in MANIFEST.MF was causing loading failure. This was when I was trying to launch a very simply scala program:

Incorrect:

Main-Class: jarek.ResourceCache
Class-Path: D:/lang/scala/lib/scala-library.jar

Correct:

Main-Class: jarek.ResourceCache
Class-Path: file:///D:/lang/scala/lib/scala-library.jar

With an incorrect version, I was getting a cryptic message, the same the OP did. Probably it should say something like malformed url exception while parsing manifest file.

Using an absolute path in the manifest file is what IntelliJ uses to provide a long classpath for a program.

Answer 8

At least the way I've done this is as follows:

If you have a nested src tree (say com.test.myclass.MyClass) and you are compiling from a root directory you need to do the following:

1) when you create the jar (usually put this in a script): jar -cvfm my.jar com/test/myclass/manifest.txt com/test/myclass/MyClass.class

2) The manifest should look like:

Mainfest-version: 1.0 Main-Class: com.test.myclass.MyClass Class-Path: . my.jar

3) Now you can run the jar from anywhere like this:

java -jar my.jar

Hope this helps someone

Answer 9

I follow the following instruction to create a executable .jar in Eclipse. Then Run command "java -jar .jar " to launch the program.

It takes care of creating mainfest and includeing main class and library files parts for you.

http://java67.blogspot.com/2014/04/how-to-make-executable-jar-file-in-Java-Eclipse.html

Answer 10

I know this is an old question, but I had this problem recently and none of the answers helped me. However, Corral's comment on Ryan Atkinson's answer did tip me off to the problem.

I had all my compiled class files in target/classes, which are not packages in my case. I was trying to package it with jar cvfe App.jar target/classes App, from the root directory of my project, as my App class was in the default unnamed package.

This doesn't work, as the newly created App.jar will have the class App.class in the directory target/classes. If you try to run this jar with java -jar App.jar, it will complain that it cannot find the App class. This is because the packages inside App.jar don't match the actual packages in the project.

This could be solved by creating the jar directly from the target/classes directory, using jar cvfe App.jar . App. This is rather cumbersome in my opinion.

The simple solution is to list the folders you want to add with the -C option instead of using the default way of listing folders. So, in my case, the correct command is java cvfe App.jar App -C target/classes .. This will directly add all files in the target/classes directory to the root of App.jar, thus solving the problem.

Answer 11

I had this error because I wrote a wrong Class-Path in my MANIFEST.MF

Answer 12

I have received the same error message after transferring the jar file by FTP and forgot to set it binary mode.

Answer 13

I have one incorret class-path librarie and solve same error