Java Swing program does not open window outside of NetBeans, but remains open in processes

My problem is that I did a Java program in NetBeans and it works normally, but the problem is that when I open the .jar outside the IDE, the window is not opened.

Here is a simple code with the same problem:

package bbb;
import javax.swing.*;

public class NewFrame extends JFrame{
    public NewFrame() {
        initComponents();
    }
    private void initComponents() {
        jButton1 = new JButton();

        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        setResizable(false);
        setSize(new java.awt.Dimension(700, 400));

        jButton1.setText("btn");

        GroupLayout layout = new GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGap(305, 305, 305)
                .addComponent(jButton1)
                .addContainerGap(319, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(GroupLayout.Alignment.LEADING)
            .addGroup(GroupLayout.Alignment.TRAILING,layout.createSequentialGroup()
              .addContainerGap(228, Short.MAX_VALUE)
              .addComponent(jButton1)
              .addGap(217, 217, 217))
        );

        ImageIcon icon = new ImageIcon(getClass().getResource("/bbb/btn.png"));
        jButton1.setIcon(icon);

        pack();
    }

    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(() -> {
            new NewFrame().setVisible(true);
        });
    }

    private JButton jButton1; 
}

Some details:

• The NewFrame class is already the primary one;
• I have already put a folder with the same package name, in the same directory, with the same images;
• If I leave the button with no icon, .jar opens normally;
• The program normally opens in NetBeans (with or without an icon);
• Also tried to open cmd (unsuccessfully);
• The .jar does not open the window (JFrame), but it appears open in the background in the Task Manager.

Please help me. I do not know what else to do ;-; .