start with this, then add your bits of code - small
sections at a time. Compile/run after each addition,
eventually you will find the part that breaks what
is supposed to happen

import javax.swing.*;
import java.awt.*;
class Testing extends JFrame
{
 public Testing()
 {
   setSize(300,200);
   setDefaultCloseOperation(EXIT_ON_CLOSE);
   setLocation(400,200);
   JPanel p1 = new JPanel();
   p1.add(new JLabel("Hello"));
   JPanel p2 = new JPanel();
   p2.add(new JLabel("World"));
   JSplitPane spt= new JSplitPane(JSplitPane.VERTICAL_SPLIT,p1,p2);
   getContentPane().add(spt);
   setVisible(true);
   spt.setDividerLocation(1.0);
 }
 public static void main( String args[] ){new Testing();}
}