Compiling and running Java from the command line

Question

I created the below project structure.

[~/Projects/CountWords]@Ubuntu1804  #> find .
.
./bin
./src
./src/main
./src/main/java
./src/main/java/App.java

This is App.java content :

package src.main.java;


public class App {
    public static void main(String[] args){
        System.out.println("Hola");
    }
}

I compile my app as :

javac -d bin/ -cp src/main/java/ src/main/java/*

Which works fine. I am using an asterisk because I'll have more classes in that folder but I have only that one for now. This creates the following structure :

[~/Projects/CountWords]@Ubuntu1804  #> find .
.
./bin
./bin/src
./bin/src/main
./bin/src/main/java
./bin/src/main/java/App.class
./src
./src/main
./src/main/java
./src/main/java/App.java

But my problem is when I try to run the app. I assumed this would work :

java src.main.java.App

But this fails with :

Error: Could not find or load main class src.main.java.App
Caused by: java.lang.ClassNotFoundException: src.main.java.App

What am I doing wrong?

I know that it must be a very silly question, but I want to code a small/medium project by hand just to understand what the IDE does on its own. After working with Java for a while using Eclipse, I noticed I had no idea how to do this by hand and I want to change that.

At the root level. Which is /home/matias/Projects/CountWords. If I try to do this : java -cp bin/ src.main.java.App I get this error : — Matias Barrios
– Matias Barrios, Commented Feb 26, 2020 at 16:52
Error: Main method not found in class src.main.java.App, please define the main method as: public static void main(String[] args) or a JavaFX application class must extend javafx.application.Application — Matias Barrios
– Matias Barrios, Commented Feb 26, 2020 at 16:52

Sergej Masljukow · Accepted Answer · 2020-02-26 17:42:57Z

1

You have to define class path for java. There are two possibilites:

run

java -cp ./bin src.main.java.App

or change to bin directory and then run without cp

cd bin 
java src.main.java.App

answered Feb 26, 2020 at 17:42

Sergej Masljukow

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3 Comments

Matias Barrios Over a year ago

Error: Main method not found in class src.main.java.App, please define the main method as: public static void main(String[] args) or a JavaFX application class must extend javafx.application.Application

Sergej Masljukow Over a year ago

Do You still have the same code like posted above in your current App.java? Because I tried it out and it compiles and runs fine. I would suggest you remove everything else you have in your src/main/java and just leave App.java there and compile and execute again.

Matias Barrios Over a year ago

You are right! I rebooted and now it works! Thank you!

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