Could not find or load main class in a simple java project

Question

I have created a simple java project "DesignPatterns". I created a file FacadePattern.java with the path being ~/DesignPatterns/Structural/FacadePattern/FacadePattern.java

My FacadePattern.java class,

public class FacadePattern {
    public static void main(String args[]) {
        // Some code
    }
}

But my editor (VSCode) gives me an error at the start of the file: The declared package "" does not match the expected package "Structural.DecoratorPattern"

So upon clicking on quick fix, it added package Structural.FacadePattern; in the first line.

So the final code became

package Structural.FacadePattern;

public class FacadePattern {
    public static void main(String args[]) {
        // Some code
    }
}

But when I compile the above file using the command

javac FacadePattern.java && java FacadePattern

It is giving me the following error:

Error: Could not find or load main class FacadePattern
Caused by: java.lang.NoClassDefFoundError: Structural/FacadePattern/FacadePattern (wrong name: FacadePattern)

After searching a lot in the internet, I ran the following command:

javac -sourcefile ~/DesignPatterns FacadePattern.java && java FacadePattern

But no use, I am getting the same error.

Can anyone explain why my editor gave an error but code ran successfully before? and why wont it compile after adding "package Structural.FacadePattern;" line? and what is -sourcefile parameter in javac command? and how to run the code with successfully without errors in editor as well as the terminal?

score 2 · Accepted Answer · answered Apr 05 '22 at 16:58

2

Stick to naming rules. Package names should be lowercase only. In your case, it should be package structural.facadepattern;
Run the 'correct' class. Because your class is not inside 'the base folder' aka the 'default package', you have to prefix the class with its package name: java Structural.FacadePattern.FacadePattern or rather java structural.facadepattern.FacadePattern if you use the proper case for packages.

answered Apr 05 '22 at 16:58

JayC667

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Hi @JayC667, I tried both the ways you suggested. The first one gave me ClassNotFoundException: Structural.FacadePattern.FacadePattern and the second one (after renaming all the folders), ClassNotFoundException: structural.facadepattern.FacadePattern. – i_know_what Apr 05 '22 at 17:33
2

My bad, I was running java command inside the facadepattern package, after changing the path to root folder, it worked! Thanks a lot! – i_know_what Apr 05 '22 at 17:37

Could not find or load main class in a simple java project

1 Answers1