Finding Main Class in "Hello World" program in Java

Question

I have a seemingly simple program in Java, but when I run it, I get the error:

Error: Could not find or load main class

Here is my code.

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

I'm entirely new to the Java language, and I don't know what else to do. My program file is named "hello_world.java", and when attempting to run the program, I type in "java hello_world.java". Am I doing something fundamentally wrong? I've also attempted "java -cp hello_world", but that gave me the same error.

What am I doing wrong?

What you're doing wrong? Impossible to say, since you didn't tell us how you compile and run your code. — Tom, Mar 30 '16 at 19:42
I used a text editor to write the program, saved it as .java file, and ran it using the terminal application on a mac. What else am I supposed to do? — Jacob Marshall, Mar 30 '16 at 19:46
Your certainly executing another .class file than `HelloPrinter.class` — Yassin Hajaj, Mar 30 '16 at 19:46
Dup: [How to execute a java .class from the command line](http://stackoverflow.com/q/1279542) — Tom, Mar 30 '16 at 19:48
I'm entirely new to the Java language, and I don't know what else to do. My program file is named "hello_world.java", and when attempting to run the program, I type in "java hello_world.java". Am I doing something fundamentally wrong? I've also attempted "java -cp hello_world", but that gave me the same error. — Jacob Marshall, Mar 30 '16 at 19:48
The file must be named HelloPrinter.java if the class is HelloPrinter. See linked question. — , Mar 30 '16 at 19:49
I renamed the file to HelloPrinter.java as you recommended, but I'm still getting the same error. **Error: Could not find or load main class HelloPrinter.java** — Jacob Marshall, Mar 30 '16 at 19:52
I have read it, and I still do not understand what needs to be done. I ran "javac HelloPrinter.java" and received a new file called "HelloPrinter.class". Even after reading the duplicate question, I still do no understand what needs to be done. What obvious mistake am I making? — Jacob Marshall, Mar 30 '16 at 19:56

Magnus · Accepted Answer · 2016-03-30T20:09:01.773

-1

From what little information you've given, I'd say you're executing it the wrong way.

Make sure you run the following two commands:

javac HelloPrinter.java
java HelloPrinter

The first command compiles your source code into a .class file. The second command executes that class file.

edited Mar 30 '16 at 20:09

answered Mar 30 '16 at 19:50

Magnus

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This works. That was the fundamental, obvious mistake I was making. I'm new to this, and I really appreciate your help. – Jacob Marshall Mar 30 '16 at 19:58
@Jacob Don't forget to [accept](http://meta.stackexchange.com/questions/5234/how-does-accepting-an-answer-work) this answer if it helped you. – Tom Mar 30 '16 at 20:02

Finding Main Class in "Hello World" program in Java

1 Answers1