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?

CodePudding user response：

1. Stick to naming rules. Package names should be lowercase only. In your case, it should be package structural.facadepattern;

2. 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.