How can I run a .class file that is located in a subfolder which is not part of a package from cmd?-CodePudding

I have HelloWorld program in a package helloworld as:

package helloworld;

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello World");
    }
}

I put this HelloWorld.java file in the package folder helloworld, which is in a folder myapp as:

C:\test\myapp>dir
 Volume in drive C has no label.
 Volume Serial Number is F48A-3578

 Directory of C:\test\myapp

10/22/2021  07:28 PM    <DIR>          .
10/22/2021  07:28 PM    <DIR>          ..
10/22/2021  07:28 PM    <DIR>          helloworld
               0 File(s)              0 bytes
               3 Dir(s)  12,348,715,008 bytes free

C:\test\myapp>cd helloworld

C:\test\myapp\helloworld>dir
 Volume in drive C has no label.
 Volume Serial Number is F48A-3578

 Directory of C:\test\myapp\helloworld

10/22/2021  07:28 PM    <DIR>          .
10/22/2021  07:28 PM    <DIR>          ..
10/22/2021  07:16 PM               436 HelloWorld.class
10/22/2021  07:14 PM               148 HelloWorld.java
               2 File(s)            584 bytes
               2 Dir(s)  12,348,715,008 bytes free

C:\test\myapp\helloworld>

In CMD (Windows), I am in a folder above the myapp folder, so, I could compile it as:

C:\test>javac myapp\helloworld\HelloWorld.java

C:\test>

But, when I tried to run it as below, it failed.

C:\test>java myapp\helloworld.HelloWorld
Error: Could not find or load main class myapp\helloworld.HelloWorld
Caused by: java.lang.NoClassDefFoundError: helloworld/HelloWorld (wrong name: myapp\helloworld/HelloWorld)

Of course, if I go into the myapp folder as below I can run it.

C:\test>cd myapp

C:\test\myapp>java helloworld.HelloWorld
Hello World

C:\test\myapp>

My question is how can I run a class file located in a subfolder which is not part of a package?

CodePudding user response：

When you run java.exe, by default the classpath is only the current folder.

When you are in the parent folder, you need to add classpath explicitly

java -cp myapp helloworld.HelloWorld

CodePudding user response：

You need to mention the classpath with java command. Please refer to this link which explains the way classpath needs to be referred

https://docs.oracle.com/javase/7/docs/technotes/tools/windows/classpath.html

So the possible command should be something like

java -classpath C:\test\myapp helloworld.HelloWorld