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, Sep 26 '15 at 23:50
From which location you tried to run your command and what is structure of your classes? — Pshemo, Sep 26 '15 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, Sep 26 '15 at 23:54
package Hello; public class HelloWorld { public static void main(String[] args) { System.out.println("Hi there. How you doin?"); } } — Jeff Ciaccio, Sep 26 '15 at 23:54
Have you read this? http://stackoverflow.com/a/18093929/139985 — Stephen C, Sep 26 '15 at 23:55
If I navigate to the folder where the class file is and run java from there, shouldn't it find the class right there in that folder? — Jeff Ciaccio, Sep 27 '15 at 00:03

score 2 · Accepted Answer · answered Sep 27 '15 at 03:44

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.

score 0 · Answer 2 · answered Sep 27 '15 at 02:33

0

You must run the code outside the Hello folder

java Hello/HelloWorld

You should have HelloWorld.class inside Hello directory.

answered Sep 27 '15 at 02:33

rvillablanca

1,606
3
21
34

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 – Jeff Ciaccio Sep 28 '15 at 02:13

Cannot run java class from command line

2 Answers2