.jar file keeps giving me " could not find the main class". Program will exit

Question

I have been having problems with this on both netbeans and eclipse even with a simple file that displays a jframe with a jlabel on it. My netbeans's project properties clearly sets testing2.hihi as my Main class and I have clean and build it which produces a .jar file in my dist folder. When I double click on it, it gives me the message" could not find the main class. Program will exit." However, if I choose to run it from the command prompt "java -jar hello2.jar" it will run as normal! This is the manifest file inside the .jar file. ``` Manifest-Version: 1.0 Ant-Version: Apache Ant 1.8.3 Created-By: 1.7.0_04-b20 (Oracle Corporation) Class-Path: X-COMMENT: src/hihi Main-Class: testing2.hihi package testing2; public class hihi extends javax.swing.JFrame { /** * Creates new form hihi */ public hihi() { initComponents(); } /** * This method is called from within the constructor to initialize the form. * WARNING: Do NOT modify this code. The content of this method is always * regenerated…

Accepted Answer

I suspect that the open command registered for Jar files is not set up correctly. Here's a way to check from the command line (at least on Windows 7; I'm pretty sure it works on Windows Vista):

- Enter the command: `assoc .jar`

- It should print `.jar=jarfile`. If it is not found (highly unlikely, given your symptoms), create the entry with the command `assoc .jar=jarfile`.

- Enter the command: `ftype jarfile`

- It should print something like `"C:\Program Files\Java\jre6\bin\javaw.exe" -jar "%1" %*` (The path to `javaw.exe` might be different on your machine.)

- If it isn't defined or prints the wrong value, fix it with: `ftype jarfile="C:\Program Files\Java\jre6\bin\javaw.exe" -jar "%1" %*`

You may have to reboot, or at least open a new Windows Explorer window, to see if double-clicking on the .jar file now works.

.jar file keeps giving me " could not find the main class". Program will exit

Solution

Problem