胶水组件??

Question

import javax.swing.*;
import java.awt.*;
import javax.swing.border.*;
public class Example12_7 extends java.applet.Applet
{
Box baseBox,boxV1,boxV2,boxV3;
public void init()
{
boxV1=Box.createVerticalBox();
for(int i=1;i<=3;i++)
{
boxV1.add(new JButton("按钮"+i));
}
boxV1.add(Box.createVerticalGlue());
boxV2=Box.createVerticalBox();
boxV2.add(Box.createVerticalGlue());
for(int i=1;i<=8;i++)
{
boxV2.add(new JButton("按钮"+i));
}
boxV3=Box.createVerticalBox();
for(int i=1;i<=6;i++)
{
boxV3.add(new JButton("按钮"+i));
if(i==3)         //为啥就会空出二个小空呢?
boxV3.add(Box.createVerticalGlue());
}
baseBox=Box.createHorizontalBox();
baseBox.add(boxV1);baseBox.add(boxV2);
baseBox.add(boxV3);add(baseBox);
}
}