The JTabbedPane specs says the following about the add(Component) method:
  public Component add(Component component)
    Adds a component with a tab title defaulting to the name of the component.

The spec does not clarify what the "name" of a component means.
As the following application shows, the tab of a JTextarea that is added to
a tabbed pane has no title. The same is true if a JButton with a non-empty
title is added to the tabbed pane.

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/*
 * JTabbedPaneTest.java
 * JTabbedPane spec has incomplete info about add(Component) method
*/


import java.awt.*;
import java.awt.event.*;
import com.sun.java.swing.*;
import com.sun.java.swing.border.*;

public class JTabbedPaneTest extends JFrame implements ActionListener {
    JTabbedPane tabbedPane;
    JButton add;
    JPanel infoPanel = new JPanel();
    JPanel p1 = new JPanel();
    JPanel p2 = new JPanel();
    JPanel panel1 = new JPanel();
    JPanel panel2 = new JPanel();
    JPanel panel3 = new JPanel();
    JPanel panel4 = new JPanel();

    public JTabbedPaneTest() {
        Container c = getContentPane();
c.setLayout(new BorderLayout());

infoPanel.setLayout(new GridLayout(0,1));
        infoPanel.add(new JLabel("JTabbedPane spec has incomplete info about add(Component) method."));
        infoPanel.add(new JLabel("It does not clarify what \"name\" of a component means."));
        infoPanel.add(new JLabel(""));
        infoPanel.setBackground(Color.white);
        c.add(BorderLayout.NORTH, infoPanel);

        tabbedPane = new JTabbedPane();
        panel1.setBackground(Color.red);
        panel2.setBackground(Color.blue);
        panel3.setBackground(Color.green);
        panel4.setBackground(Color.yellow);
        tabbedPane.addTab("Red", panel1);
        tabbedPane.addTab("Blue", panel2);
        tabbedPane.addTab("Green", panel3);
        tabbedPane.addTab("Yellow", panel4);

        add = new JButton("Add component");
        add.setBackground(new Color(170,150,250));
        add.setToolTipText("Invokes JTabbedPane.add().");
        add.addActionListener(this);

        p1.setLayout(new BorderLayout());
p1.setBorder(new SoftBevelBorder(BevelBorder.LOWERED));
        p1.add(BorderLayout.CENTER, tabbedPane);
        c.add(BorderLayout.CENTER, p1);

        p2.add(add);
        p2.setBackground(Color.pink);
        c.add(BorderLayout.SOUTH, p2);
    }

    public static void main(String argv[]) {
        JFrame frame = new JTabbedPaneTest();
frame.setTitle("JTabbedPane.add() Test");
frame.pack();
frame.setSize(725,400);
frame.setVisible(true);
    }

    public void actionPerformed(ActionEvent e) {
Object source = e.getSource();

if (source == add) {
tabbedPane.add(new JTextArea("A Textarea"));
}
    }
}
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