Error: Could not find or load main class Clojure.main
When running a Clojure program, if the java virtual machine (JVM) is unable to locate the main class, it generates the Could not find or load main class Clojure.main error.
You can try one of the following options to resolve this error.
How to resolve
Ensure that clojure is installed on your system. You can download it from the
official website https://clojure.org/releases/downloads
- Verify the syntax of the command to run the clojure program. Here’s the template:
Here, thejava -cp <classpath> clojure.main -m <your-namespace>/<your-main-function><classpath>refers to the path that includes the necessary source files and other dependencies. Make sure that<your-namespace>and<your-main-function>are replaced with the correct values from the program.
Ensure that the file containing your
mainfunction should be in a directory structure that matches itsnamespace.Verify that the
<classpath>is correctly set to include the necessary clojure libraries and JAR files.
- Verify the
:gen-classdeclaration. Do not forget to add the(:gen-class)key to thenscall:(ns your.namespace (:gen-class))
Other options
You can also try a build tool like tools.deps to simplify the process of managing dependencies and running your Clojure program.
-
With Leiningen:
lein uberjar -
With
tools.deps:clj -M -m <your-namespace>/<your-main-function>
Try it yourself
Step 1: Enter the following command in the root of the project directory.
nano project.clj
Step 2: Add the following code to the file and after making the changes, press Ctrl + X to save the changes and exit the file.
(defproject my-clojure-project "0.1.0-SNAPSHOT":description "A simple project to demonstrate Clojure error":dependencies [[org.clojure/clojure "1.10.0"]]:main clojure.examples.example)
Step 3: Run the following command:
java -cp target/my-clojure-project-0.1.0-SNAPSHOT-standalone.jar clojure.main
It will generate the error. Try re-building the project with the following command, lein uberjar, and perform step 3 again.
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