removing the small arrow of Synth L&F JInternalFrame title bar (Nimbus)

im diving around google looking how to remove the small arrow of a JInternalFrame set up with a Synth(Nimbus) Look and Feel
with a Default L&F
this code removes some of property of a JInternalFrame object, leaving only the close button

Code :

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internalFrame.putClientProperty("JInternalFrame.isPalette", Boolean.TRUE);

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but switching the lookAndFeel of the components using this code, a Synth Style internal frame has a default behavior that retains a small arrow button, a Simple png image is attached, to see what it looks like

Code :

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try {
 
            for (LookAndFeelInfo info : UIManager.getInstalledLookAndFeels()) {
 
                if ("Nimbus".equals(info.getName())) {
 
                    UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (Exception e) {
 
            e.printStackTrace();
        }

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whole code for the program

Code :

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import java.beans.PropertyVetoException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JInternalFrame;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.Rectangle;
import java.awt.RenderingHints;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Color;
import java.awt.Point;
import javax.swing.UIManager;
import javax.swing.UIManager.LookAndFeelInfo;
import javax.swing.plaf.InternalFrameUI;
import javax.swing.plaf.synth.SynthInternalFrameUI;
 
public class Window {
 
    public Window() {
 
 
        try {
 
            for (LookAndFeelInfo info : UIManager.getInstalledLookAndFeels()) {
 
                if ("Nimbus".equals(info.getName())) {
 
                    UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (Exception e) {
 
            e.printStackTrace();
        }
 
        setUp();
    }
 
    public void setUp() {
 
        JFrame f = new JFrame();
        JPanel p = new JPanel(null);
        JInternalFrame internalFrame = new JInternalFrame();
 
        internalFrame.setSize(200, 150);
        internalFrame.setOpaque(true);
        internalFrame.setLocation(new Point(50 ,2));
        internalFrame.putClientProperty("JInternalFrame.isPalette", Boolean.TRUE);    
        internalFrame.setClosable(true);
        internalFrame.setResizable(true);
        internalFrame.setVisible(true);
        p.add(internalFrame);
        p.setBackground(Color.BLACK);
        f.add(internalFrame);
        f.getContentPane().add(p);
        f.setSize(400, 200);
        f.setLocationRelativeTo(null);
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setVisible(true);
    }
 
    public static void main(String[] args) {
 
        new Window();
    }
}

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until i found this thread on another forum, having the same problem with that arrow
java - Is it possible to remove the little dropdown arrow in a JInternalFrame? - Stack Overflow

pointing out this thing

Quote:

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InternalFrame:InternalFrameTitlePane:"InternalFram eTitlePane.menuButton".icon

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questions:
1.) is there a (maybe not an Easy way) but a considerable approach to JUST REMOVE that small arrow button of a Synth Look and Feel Internal frame?
2.) i ended up on BasicInternalFrameUI, InternalFrameUI, SynthInternalFrameUI classes, where or which of these classes should i focus on to deal with this problem?
3.) how to use this classes?, google resources gives me tons of confusing codes,

i need some guides and maybe some idea, for this one