No main found when executing jar

Question

There are two classes in the above code.

So above is my code which is working fine when I hit run in Eclipse, runs fine in Netbeans as well.

I am trying to create a standalone application, a jar file.

The error I get when I double my jar is:

Could not find the main class: NewJFrame. Program will exit. I get the following from the command promt:

E:\Java Programs\Eclipse Workspace\test3\src\test3>java testT.jar
Exception in thread "main" java.lang.NoClassDefFoundError: testT/jar
Caused by: java.lang.ClassNotFoundException: testT.jar
    at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
Could not find the main class: testT.jar.  Program will exit.

I followed the command from here: "Could not find the main class: XX. Program will exit." So this is what I am typing in the command promt to create my jar:

E:\Java Programs\Eclipse Workspace\test3\src\test3>jar cfm MyJar.jar manifest.tx
t *.class SINGLE.TXT

https://i.stack.imgur.com/ncm1q.jpg

Some shots above I took to show the process.

So I think the problem could be error when I do javac? But it builds fine and runs fine in netbeans and eclipse >< Please help.

`java testT.jar` attempts to run a class called `jar` in a package called `testT`. — Peter Lawrey, Mar 17 '12 at 15:05
What about the `maifest.mf` file? Have mentioned the main class in it? — Amir Pashazadeh, Mar 17 '12 at 15:44

score 2 · Answer 1 · edited Jun 20 '20 at 09:12

2

You need to use the -jar flag.

java -jar MyJar.jar

http://docs.oracle.com/javase/tutorial/deployment/jar/run.html says

JAR Files as Applications

You can run JAR-packaged applications with the Java interpreter. The basic command is:
java -jar jar-file
The -jar flag tells the interpreter that the application is packaged in the JAR file format. You can only specify one JAR file, which must contain all the application-specific code.

and http://docs.oracle.com/javase/tutorial/deployment/jar/modman.html explains how to put a manifest in the jar.

The m option indicates that you want to merge information from an existing file into the manifest file of the JAR file you're creating.

edited Jun 20 '20 at 09:12

Community

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answered Mar 17 '12 at 14:50

Mike Samuel

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that did not work. I got the following: http://pastebin.com/npm3ksNd Also, I want this app to be able to run by just double clicking it, because I plan to turn it into an applet. – Noman Arain Mar 17 '12 at 14:57
are you sure your main class is within the test3 package and is called NewJFrame? – Jarle Hansen Mar 17 '12 at 15:18
yes, if you look at my screenshots, you'll see that NewJFram is there and if you follow the pastebin's link you will see the main method there. – Noman Arain Mar 17 '12 at 15:31
@NomanArain, the name of your class in the `Main-Class` manifest entry should be `test3.NewJFrame` not `test3/NewJFrame`. – Mike Samuel Mar 17 '12 at 15:54
Mike I changed my mainifest to say Main-Class: test3.NewJFrame but it still gives me the same error, main cannot be found. Error: Could not find the main class: test3.NewJFrame. Program will exit. – Noman Arain Mar 17 '12 at 16:10
@NomanArain, Please extract your manifest via `jar xf MyJar.jar META-INF/MANIFEST.MF` and post its content in your question so we can help debug. – Mike Samuel Mar 17 '12 at 16:13
I have taken the code out of package, http://pastebin.com/pSrjVCeL this has the code and at the boom i pasted the manifest.mf – Noman Arain Mar 17 '12 at 16:27
@NomanArain, In your manifest, you have the line `Main-Class: NewJFrame`. That is missing a package name. – Mike Samuel Mar 17 '12 at 16:33
Mike, I took out the package from my code. So my programmed is not packaged anymore. – Noman Arain Mar 17 '12 at 16:51
Your screenshot shows CODE not .class files. You have to add the compiled files to the JAR, the source won't do you any good. – Jochen Mar 17 '12 at 18:46
@Jochen I am running this command: jar cfm MyJar.jar manifest.tx t *.class SINGLE.TXT, so it's only adding .class classes. – Noman Arain Mar 17 '12 at 20:48
Manifest-Version: 1.0 Created-By: 1.6.0_31 (Sun Microsystems Inc.) Main-Class: NewJFrame – Noman Arain Mar 18 '12 at 05:33

score 0 · Answer 2 · answered Jan 31 '14 at 16:15

0

Add

Main-class: Splash

part to Manifest file. set Main class name instead Splash

That will work...

answered Jan 31 '14 at 16:15

HackerGK

360
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score 0 · Accepted Answer · answered Mar 19 '12 at 16:07

it is now working. I have not changed anything, maybe the memory got curroupted and that is why it was giving me problems. I think restart the computer is what fixed it. But yea, I don't know for sure what was wrong, though it is working fine now. So thank you for your help guys

No main found when executing jar

3 Answers3

JAR Files as Applications