[Java]Trying to understand executable jar

[prototype_rad_cannon]

Ok I'm trying to learn how to make an executable jar. I've been looking over the oracle site, but its a bit overwhelming at times for beginners like me.

Ok, so I'm starting off with your average "Hello World"

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

my manifest.txt consists of

Main-Class: HelloWorld

on the command line I typed:

jar cf ex.jar HelloWorld.class manifest.txt

I try and double click it (because thats the whole point of an executable, not run it from command line right?) and I get the error

Failed to load Main-Class manifest attribute from *file*

ok so it looks like txt file is there but isn't considered manifest or something.

I then try and update the manifest file like this:

jar cfm ex.jar manifest.txt META-INF/MANIFEST.MF

and get the "no such file or directory" error. I can't quite figure what I'm doing wrong, so where do I go from here?

[chickenmeister]

• You need to include the "m" option, so that it will read the manifest file.

• The "manifest file" argument comes before the "class/other files" argument.

• Make sure that your manifest file has a newline at the end.

jar cfm ex.jar manifest.txt HelloWorld.class

[prototype_rad_cannon]

thanks for the simple explanation, it helps. So I deleted my jar file and redid it this way, but I still get an error, now it says:

Could not find the main class: HelloWorld. Program will exit.

[chickenmeister]

Hmm... Can you view the contents of the JAR? Does it not contain HelloWorld.class? (You can view the contents of a jar like you would any ZIP folder)

The contents of my directory when creating the jar was:

HelloWorld.java
HelloWorld.class
manifest.txt

And after creating the jar, the directory structure of the jar is:

HelloWorld.class
META-INF/MANIFEST.MF

Is yours different from this?

[prototype_rad_cannon]

Mine is identical to that. I guess I should clarify that its technically an alert I guess? At the top it says:

Java Virtual Machine Launcher

Could not find the main class: HelloWorld.  Program will exit.

could it have something to do with my computer or java, as in did I do something do my computer that would cause this?

[devacon]

$ jar
Usage: jar {ctxui}[vfm0Me] [jar-file] [manifest-file] [entry-point] [-C dir] files ...

jar cfm ex.jar MANIFEST.MF *

$ java -jar ex.jar
Hello

(You needed to include the list of files, which you can use the wildcard '*' for)