無法正確顯示JScrollPane－awesq123的部落格

無法正確顯示

package hw;

import java.awt.Container;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.HeadlessException;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.DataInputStream;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.swing.WindowConstants;

/**
*
* @author awesq
*/
public class HW extends JFrame implements ActionListener {

private final JTextArea jta = new JTextArea();
private final JLabel jlb = new JLabel("網址:");
private final JTextField jtf = new JTextField(30);
private final JButton jbt = new JButton("Browse");
// private final JScrollPane jsp = new JScrollPane(jta);
private final JScrollPane jsp = new JScrollPane();

public HW() throws HeadlessException {
jsp.setPreferredSize(new Dimension(700, 500));
jsp.add(jta);
}

/**
* @param args the command line arguments
*/
public static void main(String[] args) {
HW hw = new HW();
hw.jbt.addActionListener(hw);
Container con = hw.getContentPane();

con.setLayout(new FlowLayout());

con.add(hw.jlb);
con.add(hw.jtf);
con.add(hw.jbt);
con.add(hw.jsp);

hw.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
hw.setSize(800, 600);
hw.setVisible(true);
}

@Override
public void actionPerformed(ActionEvent e) {
try {
URL url = new URL("http://fanli7.net/a/JAVAbiancheng/JAVAzonghe/20130520/355641.html");
DataInputStream dis = new DataInputStream(url.openStream());
String str = dis.readUTF();
jta.append(str);
} catch (IOException ex) {
Logger.getLogger(HW.class.getName()).log(Level.SEVERE, null, ex);
}
}
}

可以正確顯示