Unable to run jar file

Question

MANIFEST.MF

Manifest-Version: 1.0  
Created-By: 1.7.0_01 (Oracle Corporation)  
Main-Class: useDisplay

NOTE: There is a blank line after the Main-Class

display.java

public class display  
{  
    public void displayText()
    {
       System.out.println ("In displayText");
    }
}

useDisplay.java

public class useDisplay  
{
   public static void main (String args[])  
   {
      System.out.println ("In displayText");
   }
}

I ran the following commands:

javac *java
jar cf my1.jar MANIFEST.MF *class  
java -jar my1.jar

I got the following errors:

Exception in thread "main" java.lang.NullPointerException at 
sun.launcher.LauncherHelper.getMainClassFromJar(LauncherHelper.java:399) 

at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:463)

This should be a very simple example. The program works without the jar file. I have no idea what it's complaining about.

what does javac *class do? Is that something new in Java 7? Is that a new way to compile all the java source files in a directory? I assume that's not the same as using javac display.java and javac useDisplay.java — El Guapo, Mar 19 '12 at 17:09

score 0 · Accepted Answer · answered Mar 19 '12 at 17:14

0

I believe you have to add a -m to the jar command to use the MANIFEST.MF file you are specifying

jar cfm my1.jar MANIFEST.MF *class

answered Mar 19 '12 at 17:14

El Guapo

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Oh yes, that is it. I knew it was something simple. Thank you. – tadpole Mar 19 '12 at 17:19

Unable to run jar file

1 Answers1