Cannot run java class from command line

Question

I created a package in Eclipse and ran my HelloWorld just fine from Eclipse.

When I went to a command prompt and navigated to that folder and ran javac HelloWorld.java, it compilied without issue.

When I ran java HelloWorld, I got Error: Could not find or load main class HelloWorld

I also tried java Hello.HelloWorld thinking that it might be because it had a package declaration

package Hello; 
public class HelloWorld { 
    public static void main(String[] args) { 
       System.out.println("Hi there. How you doin?");
   } 
}

Add the code to your question. Without it, it's hard to know if you have a package declaration, and if you have a proper main. — RealSkeptic
– RealSkeptic, Commented Sep 26, 2015 at 23:50
From which location you tried to run your command and what is structure of your classes? — Pshemo
– Pshemo, Commented Sep 26, 2015 at 23:52
OH!! I think I've got it. When I declare package Hello; java looks for a folder named Hello under the current folder. — Jeff Ciaccio
– Jeff Ciaccio, Commented Sep 26, 2015 at 23:54
package Hello; public class HelloWorld { public static void main(String[] args) { System.out.println("Hi there. How you doin?"); } } — Jeff Ciaccio
– Jeff Ciaccio, Commented Sep 26, 2015 at 23:54

James Jithin · Accepted Answer · 2015-09-27 03:44:17Z

2

When you run javac, use the switch -d to specify that you would like to create the folder structure for package. javac reference.

E.g. javac -d . HelloWorld.java

When you say -d ., compiler creates the classes with package directory structure in the current path.

Once you have the compiled classes, use java Hello.HelloWorld to run the program.

Suggests you to start the package name with lower case.

answered Sep 27, 2015 at 3:44

James Jithin

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Comments

rvillablanca · Accepted Answer · 2015-09-27 02:33:11Z

0

You must run the code outside the Hello folder

java Hello/HelloWorld

You should have HelloWorld.class inside Hello directory.

answered Sep 27, 2015 at 2:33

rvillablanca

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1 Comment

Jeff Ciaccio Over a year ago

Thanks all!!! I realized I had to first create the classes folder in Windows before running the -d switch. I also was running java from within the folder where the class was. Going up a folder and giving it the relative path did the trick! Thanks again! @rvillablanca

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