I get the error "Failed to load Main-Class manifest attribute" when trying to run a JAR file
You may have created the project as a "class library" instead of as an "application".
To convert it, create a file manifest.mf in the project directory (can just contain Manifest-Version: 1.0 and nothing else), and make sure project.properties contains:
Then make sure you set a main class for the project in the properties dialog and select Build->Clean and Build Project. The Main-Class attribute, and any required Class-Path, will be inserted into the JAR's manifest by the build process.
Applies to: NetBeans 6.x, 7.x