Hello, I just started with Java and here’s my first problem. I get the message “cannot find or load the main class” followed by the class name when I run the “JAVA” command in the command prompt. I first compiled the .java file with the JAVAC command. No errors were reported when executing this command. Since I’m just starting, I’m not really sure if it’s right or wrong, but here is my very small first program (source code): public class HelloImad { public static void main(String[] args) { int i = 0; while (i < 5) { System.out.println("Hello World !"); i++; } } } Please help me.

unable to find or load the class : CCM

Réponse 1 / 9

MagicSonic Posted messages 1 Status Membre 6

Hi everyone!

I might be able to help you because my problem was similar to yours... (compilation works but execution won't start: "I can't find the static function or the class that contains it blablabla" <- I don't care, it just has to work!).

For everything to work properly, you need to check the following points:

Your PATH variable properly contains the path to the bin folder of the JDK (for me it's "C:\Program Files\Java\jdk1.6.0_45\bin"). It's fine on your side since you were able to compile (if you get an error message saying that javac, java... cannot be found or is not a recognized command, your first issue comes from here).
A simple thing, but make sure that your class containing the public static main function is indeed public (the compiler won’t tell you anything :/):

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

Finally, the commands to execute for compiling everything are (on Windows):

cd TheFolderContainingYourClasses // For me cd Desktop\TestJava java -cp "%cd%" YourClassName // In the example it’s Main (without the class!)

The first command places you in the folder where your .class files (obtained from compiling using javac) are located. This is essential.

The second command starts the execution. The cp flag means classpath (this way we explicitly tell Java where our .class files are). The value "%cd%" is the absolute path to the folder TheFolderContainingYourClasses (I put it in quotes because otherwise the command is misinterpreted).
Then YourClassName is the .class file containing the static main function.

There you go, I hope I was able to help you or that it can help others.

Have a nice day everyone!

Réponse 2 / 9

KX Posted messages 19031 Status Modérateur 3 020

You say you compile in the command prompt, so you must be in a specific folder, and it shouldn't be just anywhere, but in the folder where the .class file is located (the one obtained after compilation). You should thus have:

cd C:\...\workspace\ javac HelloImad.java java HelloImad

--
Trust does not exclude control.

bilach Posted messages 4 Status Membre 2

Thank you, thanks to you I've found the solution.
Thank you very much.

Réponse 3 / 9

Ghaffe Posted messages 2 Status Membre 5

Hello I think I know the source of the problem!!

Actually, for those who code in an IDE like Netbeans or others, running Javac on the class and the java does not compile.

But if you move the .java file to another folder, it compiles as it should

It's the IDE that is causing it not to compile!

KX Posted messages 19031 Status Modérateur 3 020

Hello,

On one hand, this discussion has been resolved for over two and a half years, on the other hand, there was no mention of IDE but of the command prompt...

Ghaffe Posted messages 2 Status Membre 5

I just had the same problem and it was the IDE that made it so after the javac on the class, the java command wouldn't work.

fff

2 years later, it may have been useful, and I think there are still people who have this problem, so this discussion is not resolved.

KX Posted messages 19031 Status Modérateur 3 020 > fff

"this discussion is not resolved"
The discussion has been resolved since March 23, 2012 at 9:40 PM, when bilach found the solution to his problem...

"there are people who still have this problem"
We are here in a support forum, we help people resolve their issues, we cannot prevent them from having any...

Réponse 4 / 9

Roigouny Posted messages 2 Status Membre 5

Hello everyone,
I am really happy that this topic wasn't closed too quickly; in my opinion, the correct answer is the one that suggests removing the line package xxx at the beginning of the file to be compiled.
Best wishes.
El Roigouny.

xserj Posted messages 1 Status Membre

Hi
Just removing the line package xxx at the beginning of the file to compile solves the problem, but creates an error message in Eclipse.

KX Posted messages 19031 Status Modérateur 3 020

What is important to understand is the relationship between the logical structure of the code (package/class name) and the physical structure of the files (and folders).

The following code must be in a file called "C.java" in a folder called "a" and under a subfolder called "b"

package a.b; public class C {}

It must then be used as follows:

Compilation: javac a/b/C.java
Execution: java a.b.C

Réponse 5 / 9

a

I solved the same problem by correcting my environment variables, namely CLASSPATH and Path. Maybe your problem comes from there.

dekra

I have the same problem, and I've tried both solutions, but it didn't work.

AchilloDTFA Posted messages 4 Status Membre

What should I correct in the classpath or the path?
I am in the right folder, the compilation command has no issues but the execution is causing the reported problem.
So my issue is not the folder, what could it be?

wilkoya Posted messages 1 Status Membre

I have the same problem as you @AchilloDTFA, good files, perfect compilation, but the same issue at runtime. Did you find the solution?

ben

Regarding the environment variables, you should have the following:
JAVA_HOME=path_to_the_jdk
PATH=%JAVA_HOME%\bin

To run the class from the command prompt, there are two possibilities:

1) you navigate to the same directory as the compiled class

2) Otherwise, if you want to run the program regardless of where (regardless of the directory) you make the call, you need to ensure that the JVM can see the class. To do this, you must assign the directory containing the class to the CLASSPATH variable.

Suppose your class is in the directory c:\demo\Demo.java
Suppose you are located in the directory c:\

So

2.1) you compile => javac c:\demo\Demo.java
2.2) you assign the CLASSPATH variable => set CLASSPATH=c:\demo
2.3) you execute => java Demo

Réponse 6 / 9

espoir

hello

just type: java filename

without adding the .class extension to the filename:

example: javac tp1.java

this generates the tp1.class file

then you type: java tp1

just like that

Réponse 7 / 9

wassimbkd Posted messages 1 Status Membre 4

You probably need to remove the line "package XXX;" at the beginning of the java file.

limix429

That's exactly it, it's the line package XXX that is causing a problem on my end, I can't say why, but in any case, once it's in the default package, it works.

Réponse 8 / 9

cedaimant

In the directory of the file HelloImad.class

java HelloImad

and not

java HelloImad.class

(I'm posting this because it's referenced at the top of Google.)

Réponse 9 / 9

KX Posted messages 19031 Status Modérateur 3 020

Is the class public and does it have a main method?
--
Trust does not exclude control.

bilach Posted messages 4 Status Membre 2

Since I just started, I don't really know if yes or no, but here is my very small first program (source code):

public class HelloImad {
public static void main(String[] args) {
int i = 0;
while (i < 5) {
System.out.println("Hello World !");
i++;
}
}
}

KX Posted messages 19031 Status Modérateur 3 020

You must not be in the right folder then.
You need to be in the folder where the file HelloImad.class is located.
--
Trust does not exclude control.

bilach Posted messages 4 Status Membre 2

I didn't quite understand your response because even when I dragged the created class into the command prompt, the error message is still the same!!

Unable to find or load the class

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