怎么样在开始接收的文本域添加一个滚动条？

import java.io.IOException;
import java.net.*;
public class Notification extends Thread{
    String weather="节目预报：八点有大型晚会，请收听";
    int port=9898;
    InetAddress iaddress=null;
    MulticastSocket socket=null;
    Notification(){
        try {
            iaddress=InetAddress.getByName("224.255.10.0");
            socket=new MulticastSocket(port);
            socket.setTimeToLive(1);
            socket.joinGroup(iaddress);
        }catch(IOException e)
        {
            e.printStackTrace();
        }
    }
    public void run()
    {
        while(true) {
            DatagramPacket packet=null;
            byte data[]=weather.getBytes();
            packet=new DatagramPacket(data,data.length,iaddress,port);
            System.out.println(weather);
            try {
                socket.send(packet);
                sleep(3000);
                
            }catch(IOException e)
            {
                e.printStackTrace();
            }catch(InterruptedException e)
            {
                e.printStackTrace();
            }
        }
    }
    
            

    public static void main(String[] args) {
        Notification w=new Notification();
        w.start();

    }

}

import java.awt.*;
import java.awt.event.*;
import java.io.IOException;
import java.net.*;
import javax.swing.*;
public class Receive extends JFrame implements Runnable,ActionListener{
    int port;
    InetAddress group=null;
    MulticastSocket socket=null;
    JButton inceBtn=new JButton("停止接收");
    JButton stopBtn=new JButton("开始接收");    
    JTextArea inceAr=new JTextArea(10,10);
    JTextArea inced=new JTextArea(10,10);
    Thread thread;
    boolean stop=false;
    public Receive()
    {
        setTitle("广播数据报");
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        thread=new Thread(this);
        inceBtn.addActionListener(this);
        stopBtn.addActionListener(this);
        inceAr.setForeground(Color.blue);
        JPanel north=new JPanel();
        north.add(inceBtn);
        north.add(stopBtn);
        add(north,BorderLayout.NORTH);
        JPanel center=new JPanel();
        center.setLayout(new GridLayout(1,2));
        center.add(inceAr);
        center.add(inced);
        add(center,BorderLayout.CENTER);
        
        validate();
        port=9898;
        
    
    
    
        try {
            group=InetAddress.getByName("224.255.10.0");
            socket=new MulticastSocket(port);
            socket.joinGroup(group);
        }catch(IOException e)
        {
            e.printStackTrace();
        }
        setBounds(100,50,360,380);
        setVisible(true);
        
    }
    public void run()
    {
        while(!stop) {
            byte data[]=new byte[1024];
            DatagramPacket packet=null;
            packet=new DatagramPacket(data,data.length,group,port);
            try {
                socket.receive(packet);
                String message=new String(packet.getData(),0,packet.getLength());
                inceAr.setText("正式接收的内容：\n"+message);
                inced.append(message+"\n");
            }catch(IOException e)
            {
                e.printStackTrace();
            }
        }
    }
    public void actionPerformed(ActionEvent e)
    {
        
    if(e.getSource()==inceBtn)
    {
        inceBtn.setBackground(Color.red);
        stopBtn.setBackground(Color.yellow );
        if(!(thread.isAlive()))
        {
            thread=new Thread(this);
        }
        thread.start();
        stop=false;
        
    }
    if(e.getSource()==stopBtn)
    {
        inceBtn.setBackground(Color.yellow);
        stopBtn.setBackground(Color.red);
        stop=true;
    }
    
    }
    
    

    public static void main(String[] args) {
        Receive rec=new Receive();
        rec.setSize(460,200);
    }

}

inceAr.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
inceAr.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED);