Main entry point class 'HelloWorld.java' neither found on... on M2

[SimoneGiusso]

Describe the issue

Error: Main entry point class 'src/main/java/org/simonegiusso/buildtimeinizialization/HelloWorld.java' neither found on
classpath: '/Users/simonegiusso/Dev/GithubProjects/graalvm' nor
modulepath: '/Users/simonegiusso/.sdkman/candidates/java/21.0.1-graal/lib/svm/graal-microservices.jar:/Users/simonegiusso/.sdkman/candidates/java/21.0.1-graal/lib/svm/library-support.jar'.

When running:

native-image src/main/java/org/simonegiusso/buildtimeinizialization/HelloWorld.java

Steps to reproduce the issue
Run the above command on this class:

package org.simonegiusso.buildtimeinizialization;

public final class HelloWorld {
    private HelloWorld() {}

    public static void main(final String[] args) {
        Greeter.greet();
    }

    private enum Greeter {
        ;

        static {
            System.out.println("Greeter is getting ready!");
        }

        static void greet() {
            System.out.println("Hello, World!");
        }
    }
}

Describe GraalVM and your environment:
Model Name: MacBook Air
Chip: Apple M2
Total Number of Cores: 8 (4 performance and 4 efficiency)
Memory: 16 GB
System Firmware Version: 10151.81.1
Operating System: macOS Sonoma 14.3.1

$java -version
java version "21.0.1" 2023-10-17
Java(TM) SE Runtime Environment Oracle GraalVM 21.0.1+12.1 (build 21.0.1+12-jvmci-23.1-b19)
Java HotSpot(TM) 64-Bit Server VM Oracle GraalVM 21.0.1+12.1 (build 21.0.1+12-jvmci-23.1-b19, mixed mode, sharing)

If I replace native-image with javac it compiles.

[meuzame]

I believe you have to specify a .class file instead of a .java file as an argument to native-image
native-image usage is

Usage: native-image [options] class [imagename] [options]
           (to build an image for a class)
   or  native-image [options] -jar jarfile [imagename] [options]
           (to build an image for a jar file)
   or  native-image [options] -m <module>[/<mainclass>] [options]
       native-image [options] --module <module>[/<mainclass>] [options]
           (to build an image for a module)

So first running
javac src/main/java/org/simonegiusso/buildtimeinizialization/HelloWorld.java
and then
native-image src/main/java/org/simonegiusso/buildtimeinizialization/HelloWorld.class
should work

[SimoneGiusso]

So first running javac src/main/java/org/simonegiusso/buildtimeinizialization/HelloWorld.java and then native-image src/main/java/org/simonegiusso/buildtimeinizialization/HelloWorld.class should work

Unfortunately not:

[fniephaus]

Hi @SimoneGiusso,
What you would typically do on HotSpot is:

javac src/main/java/org/simonegiusso/buildtimeinizialization/HelloWorld.java
java -cp ./src/main/java org.simonegiusso.buildtimeinizialization.HelloWorld

Note there is no file extension when running java because it is referring to the HelloWorld call, which contains the static main method. For it to be picked up, you should be able to just put ./src on the classpath. native-image is designed to be a drop-in replacement for java, so you would run this instead:

javac src/main/java/org/simonegiusso/buildtimeinizialization/HelloWorld.java
native-image -cp ./src/main/java org.simonegiusso.buildtimeinizialization.HelloWorld
./helloworld

The native-image command generates an executable for your HelloWorld app, and ./helloworld runs it.

Hope this helps!

[SimoneGiusso]

Hope this helps!

@fniephaus Always stuck with the same error:

[fniephaus]

In you example, you actually need to use -cp src/main/java due to the directory structure you have set up. My point is still the same though: first, make sure you can run your example on java, then replace java with native-image to generate an executable.