JLabel moved when I type text

Question

Using BoxLayout I have placed a JLabel on top of a JTextArea. Now, when I type text in the JTextArea, the JLabel moves.
Why does this happen, and what can I do to prevent it?
This is my code:
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class T2 {
    public static void main(String[] args) {
     try {
         javax.swing.SwingUtilities.invokeAndWait(new Runnable() {
              public void run() {
               JFrame mainw = new JFrame("T2");
               mainw.addWindowListener(new WindowAdapter() {
                    public void windowClosing(WindowEvent e) {
                        System.exit(0);
               JComponent pane = (JComponent)mainw.getContentPane();
               pane.setLayout(new BoxLayout(pane,BoxLayout.Y_AXIS));
               pane.add(new JLabel("Write something here:"));
               pane.add(new JTextArea(10,30));
               mainw.setSize(200, 200);
               mainw.setVisible(true);
     catch (Exception e) {
         System.err.println("Exception: " + e);
}

Answer 1

Why does this happen, Read the Swing tutorial on [How to Use Box Layout|http://java.sun.com/docs/books/tutorial/uiswing/TOC.html]. It explains how components are aligned when the "X alignment" of compnents is different, which they are in your case (run the code below to see the output). So what is happening is the the label is being aligned to the center of the text area "preferred size" and the preferred size changes as you add text to it.
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class T2 {
    public static void main(String[] args) {
     try {
         javax.swing.SwingUtilities.invokeAndWait(new Runnable() {
              public void run() {
               JFrame mainw = new JFrame("T2");
               mainw.addWindowListener(new WindowAdapter() {
                    public void windowClosing(WindowEvent e) {
                        System.exit(0);
               JComponent pane = (JComponent)mainw.getContentPane();
               pane.setLayout(new BoxLayout(pane,BoxLayout.Y_AXIS));
               JLabel label = new JLabel("Write something here:");
               System.out.println(label.getAlignmentX());
               pane.add(label);
               JTextArea textArea = new JTextArea(10,30);
               System.out.println(textArea.getAlignmentX());
//               textArea.setAlignmentX(0.0f);
               pane.add(textArea);
               mainw.setSize(200, 200);
               mainw.setVisible(true);
     catch (Exception e) {
         System.err.println("Exception: " + e);
and what can I do to prevent it?Standardize the alignments:
textArea.setAlignmentX(0.0f);