Spec says setIconAt(index,Icon) adds an Icon to TabbedPane index. What I get when I implement this is an Icon for the TabbedPane as well as the same icon for the disabled state of the tab index. This is incorrect. I did not ask or set the disabledIcon.

Spec for: setIconAt

public void setIconAt(int index, Icon icon)

   Sets the icon at index to icon which can be null. An internal exception is
raised if there is no tab at that index.
 Parameters:
    index - the tab index where the icon should be set
    icon - the icon to be displayed in the tab

TestCase for this:

Press Blue Test 1 button several times. You will see an icon for the enabled state and the same icon for the disabled state, not as spec'd

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;
import javax.accessibility.*;

public class SetDisabledIconAt extends JFrame implements ActionListener{
  String path;
  boolean state = true;
  Container contentPane = getContentPane();
  JTabbedPane jtp = new JTabbedPane();
  JPanel panelOne = new JPanel();
  JPanel panelTwo = new JPanel();
  
  private JPanel buttonPanel = new JPanel();
  private JPanel bottomPanel = new JPanel(new BorderLayout());
  private JPanel statusPanel = new JPanel();
  Object obj;
  
  private JLabel label = new JLabel("Press Blue \"Test 1\" button to start test.");
  private JButton start, start1, start2, start3;
  private JButton pass;
  private JButton fail;

  SetDisabledIconAt(String workDir) {
    super("setDisabledIconAt() Test");

    // Add Invoke Buttons
    start = addButton(buttonPanel,"Test 1",Color.blue);
    pass = addButton(buttonPanel,"Pass",Color.green);
    fail = addButton(buttonPanel,"Fail",Color.red);
    bottomPanel.add(buttonPanel,BorderLayout.NORTH);
    statusPanel.add(label);
    bottomPanel.add(statusPanel,BorderLayout.SOUTH);

    contentPane.add(bottomPanel,BorderLayout.SOUTH);
    // Add all the Tabs to your TabbedPane
    jtp.add("Panel One", new JPanel());
    
    // The folowing 2 lines create an ImageIcon for tab and a disabled Icon
    // this is a bug. Doc does not specify this.
    jtp.add("Panel Two", new JPanel());
    jtp.setIconAt(1,new ImageIcon(workDir+"/rocketsm.gif"));
    
    // uncomment line below create an ImageIcon for Tab and not a disabled icon.
    //jtp.addTab("Panel Two",new ImageIcon(workDir+"/rocketsm.gif"), new JPanel());
    
    
    contentPane.add(jtp,BorderLayout.CENTER);

    // Icon icon1 = jtp.getIconAt(1);
    // Below line is for null icon to be drawn no recalculation needs to be done.
    //jtp.setDisabledIconAt(0,null);
    // Below line requires recalculation of tab because there is a disabled icon assocciated with it.
    // jtp.setDisabledIconAt(0,icon1);

    // These next two lines add a disabled icon to tab 2
    //Icon icon2 = jtp.getDisabledIconAt(0);
    //jtp.setDisabledIconAt(1,icon2);
  
    // Add Window handler
    addWindowListener(new WindowAdapter(){
      public void windowClosing(WindowEvent event){ System.exit(0);}
    });
  }

  public void actionPerformed(ActionEvent evt) {
    String cmd = evt.getActionCommand();
    if (evt.getSource() == pass) {
      System.out.println("Test Passed");
      System.exit(0);
    }
    else if (evt.getSource() == fail) {
      System.out.println("Test Failed");
      System.exit(1);
    }
    else if (evt.getSource() == start) {
      jtp.setEnabledAt(0,state);
      jtp.setEnabledAt(1,!state);
      if(state) {
label.setText("Is \"Panel One\" Enabled and \"Panel Two\" Disabled, and imageIcon should not be there as well.?");
state = false;
// I needed to add this line because the bounds for the tab changed
// since JDK does not re-calculate the bounds until the next tab press or
// window re-size.
jtp.updateUI();
      }
      else {
label.setText("Is \"Panel One\" Disabled and \"Panel Two\" Enabled, and display an Icon?");
state = true;
// I needed to add this line because the bounds for the tab changed
// since JDK does not re-calculate the bounds until the next tab press or
// window re-size.
jtp.updateUI();
      }
    }
  }
  
  public JButton addButton(JPanel addComponent, String name, Color color) {
    JButton b = new JButton(name);
    b.setBackground(color);
    b.addActionListener(this);
    addComponent.add(b);
    return b;
  }

  public static void main(String[] args) {
     String workDir = "";
    if (args.length != 0)
      workDir = args[0];
    else
      workDir = System.getProperty("user.dir");
    // Launch Test with workDir location. Location to find gif files.
    SetDisabledIconAt t = new SetDisabledIconAt(workDir);
    t.setSize(700,150);
    t.setVisible(true);
  }
}