Java and Gradle - Build failed with an exception

Question

I want to simply debug hello Java, but some gradual error is causing failure while debugging my code.

package learning.javalearning;   
    public class demo {
        public static void main(String[] args) {
            System.out.println("Hello J");
    }
}

FAILURE: Build failed with an exception.

• Where: Initialization script 'C:\Users\JERRI._PC\AppData\Local\Temp\demo_main__.gradle' line: 20

• What went wrong: A problem occurred configuring project ':app'. Could not create task ':app:demo.main()'. SourceSet with name 'main' not found.

• Try: Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.