Make pattern in swing with package

package work;

import java.io.*;

public class pack1
{

public static String make(int n)
{
String s="";
int i,j,k;
for(i=0; i<n;i++)
{
for(k=n-i-1;k>=0;k--)
s=s+" ";

for(j=0;j<=i*2+1;j++)
s=s+"*";
s+="\n";
}
return s;


}
}




import java.applet.*;
import javax.swing.*;
import javax.swing.event.*;
import java.awt.event.*;
import java.awt.*;
import java.io.*;
import java.lang.*;
import work.pack1;

public class a2 implements ActionListener
{
JButton b1,b2;
JFrame jf;
JTextArea jta;
JScrollPane  jsp;
JTextField jtf;
JToolBar jtb;
a2()
{
frame();
button();
text();
jf.setVisible(true);
tool();

}

public void button()
{
b1=new JButton("pattern");
b2=new JButton("clear");
b1.addActionListener(this);
b2.addActionListener(this);
}
public void tool()
{
jtb=new JToolBar();

jtb.add(b1);
jtb.add(b2);
jtb.add(jtf);
jf.add(jtb,BorderLayout.NORTH);

}

public void frame()
{
jf=new JFrame(" pattern maker");
jf.setSize(100,300);
}
public void text()
{
jta=new JTextArea();
jsp =new JScrollPane(jta);

jtf=new JTextField();
jta.setEditable(false);
jta.setSize(80,200);
jf.add(jsp,BorderLayout.CENTER);
}

public void actionPerformed(ActionEvent ae)
{
if(ae.getActionCommand().equals(b1.getText()))
{
try
{
jta.setText(pack1.make(Integer.parseInt(jtf.getText())));
}
catch(Exception e)
{
}
}
if(ae.getActionCommand().equals(b2.getText()))
{
jta.setText("");
}

}
public static void main(String args[])throws Exception
{
SwingUtilities.invokeLater( new Runnable()
{
public void run()
{
new a2();
}
}
);
}



}