Why does the last JLabel I add to the JFrame move if I resize the window by dragging the corner with the mouse? - resize

Question

When I run this program, the panel with the 6 buttons appears as it should on the bottom of the screen, and the first 3 labels appear as they should and where they should, but the last label appears at about the center of the screen. Furthermore, when I click and drag on the bottom right corner of the window (resizing the window), the panel and the last label move so they stay in their relative positions with the size of the window but the first 3 labels stay in their designated positions. When I uncomment the line of code towards the bottom that adds a blank JLabel, all 4 labels are now in their correct spots and only the panel moves when I resize the window. Could someone please explain what is going on here? Thanks in advance!
import javax.swing.*;
import java.awt.*;
public class X extends JFrame{
private JPanel panel;
private JButton buttons[];
private JLabel labels[];
private Icon images[];
public X()
{
panel = new JPanel();
panel.setPreferredSize(new Dimension(470,110));
buttons = new JButton[6];
labels = new JLabel[4];
Dimension dim = new Dimension(75,100);
labels = new JLabel[4];
images = new Icon[6];
for(int i = 0; i<6;i++)
images[i] = new ImageIcon(getClass().getResource("image" + i + ".gif"));
int j = 5;
while( j >= 0 ){
Icon image = images[j];
buttons[j] = new JButton(image);
buttons[j].setPreferredSize(dim);
panel.add(buttons[j]);
j--;
}
add(panel, BorderLayout.SOUTH);
j = 3;
while( j>=0){
Icon image = new ImageIcon(getClass().getResource("image6.gif"));
labels[j] = new JLabel(image);
labels[j].setPreferredSize(dim);
if (j==3){
labels[j].setBounds(200,135,75,100);
}
else if (j==2){
labels[j].setBounds(313,70,75,100);
}
else if (j==1){
labels[j].setBounds(425,135,75,100);
}
else if (j==0){
labels[j].setBounds(313,200,75,100);
}
add(labels[j]);
j--;
}
// add(new JLabel());
}
public static void main(String[] args) {
X frame = new X();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(700,500);
frame.setVisible(true);
}
}

Answer 1

1) You should read Javadocs for JPanel/JButton/JLabel and their default behaviours.
2) You should make sure that the code which you post compiles
3) You should make sure that the code AS you post it illustrates your problem
As it is your post does not meet requirements 2) and 3) and you probably did not read enough of 1)