关于JSplitPane的分割位置.

咨询一下,JSplitPane的分割位置怎么设定?我在程序注释了.我修改了,可是
没有变化,这是怎么回事.
package src;
import javax.swing.*;
import java.awt.*;public class JSplitPanel extends JPanel{
public JSplitPanel(){
//设置布局管理器
setLayout(new BorderLayout());

JTree jt=new JTree();
String[] numArray={"One","Two","Three","Four","Five","Six","Seven","Eight","Nine","Ten"};
JList jl=new JList(numArray);

JScrollPane left=new JScrollPane(jt);
JScrollPane right=new JScrollPane(jl);

left.setMaximumSize(new Dimension(0,0));
right.setMaximumSize(new Dimension(0,0));

//分裂Pane，水平(HORIZONTAL_SPLIT)
JSplitPane pane=new JSplitPane(JSplitPane.HORIZONTAL_SPLIT,left,right);

pane.setDividerLocation(0.5);//分割位置设置???
add(pane,BorderLayout.CENTER);
}
public static void main(String[] args) {
JFrame jf=new JFrame("JSplitPanel Example");
jf.setSize(500,400);
jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

JPanel jp=new JSplitPanel();
jf.getContentPane().add(jp,BorderLayout.CENTER);
jf.setVisible(true);
}}