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

User · Answer

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".

User · Answer

Sometimes could missing the below line under  lt build gt  tag in pom xml when packaging through maven  since src folder contains your java files  lt sourceDirectory gt src lt  sourceDirectory gt

User · Answer

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

User · Answer

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

User · Answer

If you use package names  it won t work with folders containing dots  Error  Could not find or load main class   Even though it compiles and creates the jar file successfully   Instead it requires a complete folder hierarchy   Fails   com example mypackage      Main java   Works   com      example          mypackage              Main java   To compile in Linux   javac  find com  -name    java          amp  amp  jar cfe app jar com example mypackage Main  find com  -name    class

User · Answer

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

User · Answer

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

User · Answer

I had this error because I extracted JAR files from libraries to the target JAR by IntellijIDEA  When I choose another option  copy to the output directory      it solved the problem  Hope this helps you

User · Answer

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

User · Answer

in IntelliJ  I get this error when trying to add the lib folder from the main project folder to an artifact  Placing and using the lib folder in the src folder works

User · Answer

I was getting this error because my main class is in test package  and I am creating artifact using IntelliJ  After I checked the box Include Tests when creating artifact  it got resolved  Screenshot from IntelliJ showing Include Tests checkbox

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

I had the same problem due to copying and pasting code from a Microsoft Word Document  Seems there was a slightly different type of dash - character used  when I replaced the longer dash character with the correct - the program executed properly

[java] Could not find or load main class with a Jar File

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