Java中怎么改变字体的一个简单实例和运行效果

package java;
import java.awt.FlowLayout;
import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import javax.swing.*;
public class fontnameDome extends JFrame implements ActionListener
{
/**
*
*/
private static final long serialVersionUID = 1L;
JLabel jl1;
JTextArea jta;
JButton jb1,jb2;
JPanel jp;
JScrollPane js;
String name="宋体";
public fontnameDome()
{
jl1=new JLabel("留言板");
jta=new JTextArea(13,45);
jb1=new JButton("改变字体");
jb2=new JButton("提交");
jp=new JPanel();
js=new JScrollPane(jta);
jp.add(jl1);
jp.add(js);
jp.add(jb1);
jp.add(jb2);
jta.setText("同一个世界，同一个梦想！");
jta.setFont(new Font("宋体",Font.PLAIN,12));
this.add(jp);
this.setSize(330, 300);
this.setVisible(true);
jb1.addActionListener(this);
jb2.addActionListener(this);
}
public void actionPerformed(ActionEvent e)
{
if(e.getSource()==jb1)
{
final JDialog jd=new JDialog(this,"提示",true);
jd.setLayout(new FlowLayout());
ButtonGroup bg=new ButtonGroup();
JRadioButton jrb1=new JRadioButton("华文行楷");
JRadioButton jrb2=new JRadioButton("华文细黑");
JButton jb3=new JButton("确定");
bg.add(jrb1);
bg.add(jrb2);
jd.add(jrb1);
jd.add(jrb2);
jrb1.addItemListener(new ItemListener()
{
public void itemStateChanged(ItemEvent e)
{
name="华文行楷";
}
});
jrb2.addItemListener(new ItemListener()
{
public void itemStateChanged(ItemEvent e)