为什么会出现一部分显示不出来的情况，splitH上面添加了text和splitV， splitV上面添加了split1和button，为什么split1无法显示出来呢，新手，求教（理想中是左面应该是3个按钮）拜谢~~

代码如下：
import java.awt.BorderLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JSplitPane;
import javax.swing.JTextArea;
public class JSplitPaneWindow2 extends JFrame{
private JButton button1,button2,button3;
private JTextArea text;
private JSplitPane splitV,splitH,split1;
JSplitPaneWindow2(){
button1 = new JButton("Button1");
button2 = new JButton("Button2");
button3 = new JButton("Button3");
new JButton("Button4");
text = new JTextArea("Text");
splitV = new JSplitPane(JSplitPane.VERTICAL_SPLIT,true,split1,button1);
split1 = new JSplitPane(JSplitPane.VERTICAL_SPLIT,true,button2,button3);
splitH = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT,true,splitV,text);
add(splitH,BorderLayout.CENTER);
setBounds(350,300,300,200);
setVisible(true);
splitH.setDividerLocation(0.3);
setDefaultCloseOperation(this.EXIT_ON_CLOSE);
validate();
}
}
public class Example5_2_2 {
public static void main(String [] args){
JSplitPaneWindow2 window = new JSplitPaneWindow2();
}
}