How to run a simple class file from Linux shell?

Question

I am new to Java and I want to run a simple java file on my Linux host.

I started with a simple shell command:

mkdir -p ~/py4j/examples

I put AdditionApplication.java in the above folder

The file looks like this:

// ~/py4j/examples/AdditionApplication.java



package py4j.examples;



import py4j.GatewayServer;



public class AdditionApplication {



  public int addition(int first, int second) {

    return first + second;

  }



  public static void main(String[] args) {

    AdditionApplication app = new AdditionApplication();

    // app is now the gateway.entry_point

    GatewayServer server = new GatewayServer(app);

    server.start();

  }

}

Notice that it imports this:

import py4j.GatewayServer;

The above import depends on code here:

~/py4j0.10.6.jar

Next I installed java and set two env variables:

export JAVA_HOME=${HOME}/jdk

export PATH="${JAVA_HOME}/bin:${PATH}"

I use this shell command to see it:

${JAVA_HOME}/bin/java -version

It says:

java version "1.8.0_152"

Java(TM) SE Runtime Environment (build 1.8.0_152-b16)

Java HotSpot(TM) 64-Bit Server VM (build 25.152-b16, mixed mode)

Next I ran two shell commands:

cd ~

javac -cp py4j0.10.6.jar py4j/examples/AdditionApplication.java

The above command created a class file:

dan@h79:~ $ ll py4j/examples/AdditionApplication.*

-rw-rw-r-- 1 dan dan 472 Dec 22 20:59 py4j/examples/AdditionApplication.class

-rw-rw-r-- 1 dan dan 431 Dec 22 20:58 py4j/examples/AdditionApplication.java

dan@h79:~ $

Next I ran another shell command:

dan@h79:~ $ java -cp py4j0.10.6.jar py4j.examples.AdditionApplication

Error: Could not find or load main class py4j.examples.AdditionApplication

dan@h79:~ $

Question: How do I run ~/py4j/examples/AdditionApplication.class ?

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Answer 1

You need to add classpath for AdditionApplication as well.

java -cp py4j0.10.6.jar:. py4j.examples.AdditionApplication

Notice the :.. : is path separator, . is current directory. Of course that assumes current folder is ~,

How to run a simple class file from Linux shell?

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