Cross-Language Ray framework: io.ray.api.exception.RayActorException: The actor <id> died unexpectedly before finishing this task – Ubuntu

I am trying to invoke a python remote function from Java, using the exact same code as mentioned here:
https://docs.ray.io/en/latest/ray-core/cross-language.html#java-calling-python

I got this error:

root@<user>-ubuntu:/dev/Ray_Java/target# java -jar Ray_Java-1.0-SNAPSHOT-jar-with-dependencies.jar
2023-01-23 11:00:10,206 INFO RunManager [main]: Ray runtime started @<ip> .
io.ray.api.exception.RayActorException: The actor <id> died unexpectedly before finishing this task.
at io.ray.runtime.object.ObjectSerializer.deserializeActorException(ObjectSerializer.java:257)
at io.ray.runtime.object.ObjectSerializer.deserialize(ObjectSerializer.java:104)
at io.ray.runtime.object.ObjectStore.get(ObjectStore.java:140)
at io.ray.runtime.AbstractRayRuntime.get(AbstractRayRuntime.java:144)
at io.ray.runtime.AbstractRayRuntime.get(AbstractRayRuntime.java:125)
at io.ray.runtime.AbstractRayRuntime.get(AbstractRayRuntime.java:120)
at io.ray.api.Ray.get(Ray.java:98)
at io.ray.runtime.object.ObjectRefImpl.get(ObjectRefImpl.java:77)
at demo.JavaCallPythonDemo.main(JavaCallPythonDemo.java:26)

JavaCallPythonDemo.java:26 is :
Assert.assertEquals(objRef1.get(), 1);

Versions / Dependencies:

OS: Ubuntu 20.04 [LTS],
Python: 3.8.10,
Java: OpenJDK 11.0.17,
Ray: 2.2,
Apache Maven: 3.6.3

I have overwritten ray.conf file and specified run-mode as ‘CLUSTER’, and am running it in a single node cluster
I am using this in a stand-alone maven project and have specified ray-api and ray-runtime dependencies in pom.xml.
I have included maven-assembly plugin and am creating jar of this project using ‘mvn install’ and then later running this jar (having specified JavaCallPythonDemo.java as the main class).

I was able to initialize Ray from Java and run the jar generated by maven successfully. Here’s a code for the same:

package demo;

import io.ray.api.Ray;

public class RayInit {
public static void main(String args[]) {
Ray.init();
System.out.println("is ray initialized: "+Ray.isInitialized());
Ray.shutdown();
}
}