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?

Solution 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

Solution 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

Solution 3

This error comes even if you miss "-" by mistake before the word jar

Wrong command java jar test.jar

Correct command java -jar test.jar

Solution 4

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

Solution 5

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.

View more solutions