New to Java

I started Java today and am using NetBeans IDE 4.1.

package helloworldapp;

    
    public Main() {
    }
    

    public static void main(String[] args) {

       JFrame frame = new JFrame("Hello");
       frame.setsize(300, 300);
       frame.setvisible(true);
       
    }
    
}

NetBeans informs me that it 'cannot find symbol'. Help appreciated.