NetBeans IDE 8.0.2

1) Create new Java Application project
Java Platform: JDK 1.8 (JDK 1.8.0_25)

2) Add two Java files into project


public class A {
    public static void main(String[] args)
    {
        System.out.println("Hello from A");
    }
}

--

package pckg;

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;

public class ClassA {

    JButton btn = new JButton();
    
    void test() {
        btn.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                new A().sayHello();
            }
            class A {
              void sayHello() {
                  System.out.println("Hello world");
              }
            }
        });                   
    }
    
    public static void main(String[] args)
    {
        ClassA ca = new ClassA();
        ca.test();
        ca.btn.doClick();
    }
}


NetBeans underlines the local class A in method test() with error message "duplicate class A".
Well, I am aware that using default package is not standard approach to Java packages, but JDK compiler does not complain about this.

cd project_dir
mkdir bin
cd src
javac -d ../bin A.java pckg/*.java
cd ../bin
java -cp ./*.class;pckg/*.class pckg.ClassA
Hello World
java -cp ./*.class;pckg/*.class A
Hello from A