Java SE (Java Platform, Standard Edition)

I want the divider is located at the right(under) component.
run this program you will see my effect, and fix this problem. thanks for reading

import java.awt.BorderLayout;
import java.awt.FlowLayout;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JSplitPane;
import javax.swing.JTabbedPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.swing.JTree;
import javax.swing.tree.DefaultMutableTreeNode;


public class ChatFrame extends JFrame{
	private JTree tree = null;
	private ClientNode[] clientArray= new ClientNode[9999];
	private JTextArea textChat=null;
	private JTextField [] textBox = new JTextField[9999];
	private Socket connection=null;
	private BufferedReader in = null;
	private PrintWriter out = null;
	private int port;
	private JTabbedPane communicationTab;
	private JButton sendButton;
	
	public ChatFrame(int port){
		setSize(300,300);
		this.port = port;
		DefaultMutableTreeNode user = new DefaultMutableTreeNode("Another users");
		DefaultMutableTreeNode Client1 = new DefaultMutableTreeNode("Client 1");
		user.add(Client1);
		tree = new JTree(user);
		JScrollPane treeScrollPane = new JScrollPane(tree);
		JPanel p = new JPanel();
		p.add(treeScrollPane);
		communicationTab = new JTabbedPane();
		JSplitPane upperSplitPane = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT,communicationTab,p);
		upperSplitPane.setContinuousLayout(true);
		upperSplitPane.setOneTouchExpandable(true);
		upperSplitPane.setLastDividerLocation(1);
		textChat = new JTextArea();
		textChat.setLineWrap(true);
		textChat.setWrapStyleWord(true);
		JScrollPane scroll = new JScrollPane(textChat);
		JPanel q = new JPanel();
		sendButton = new  JButton("Send");
		sendButton.setSize(2,2);
		q.setLayout(new FlowLayout());		
		q.add(sendButton);
		JPanel tc = new JPanel();
		tc.setLayout(new BorderLayout());
		tc.add(scroll, BorderLayout.CENTER);
		tc.add(q,BorderLayout.EAST);
		JSplitPane underSplitPane = new JSplitPane(JSplitPane.VERTICAL_SPLIT,upperSplitPane,tc);
		underSplitPane.setLastDividerLocation(1);
		getContentPane().add(underSplitPane,"Center");
	}
	
	public void connectToServer(){
		try{
			connection = new Socket("serverName",getPort());
			while(true){
				in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
				out = new PrintWriter(connection.getOutputStream());
				String s = in.readLine();
				if(s!=null){
					textChat.append(s);
				}
			}
		}catch(Exception e){
			
		}
	}
	
	public int getPort(){
		return port;
	}
	public static void main(String[] args){
		ChatFrame c = new ChatFrame(903);
		c.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		c.show();
	}
}