Applet program to find a number is prime or not using Java

import java.applet.*;
import java.awt.*;
import java.awt.event.*;
/*

<applet code="prime.class" width="500" height="600">
</applet>

*/
public class prime extends Applet implements ActionListener
{
Label lbl1;
TextField txt1,txt2;
Button btn1;
public void init()
{
lbl1=new Label("Enter any Number : ");
txt1=new TextField(20);
txt2=new TextField(20);
btn1=new Button("Check");
setLayout(null);

txt2.setBounds(130,50,200,20);
add(txt2);
txt1.setBounds(230,100,120,20);
add(txt1);
lbl1.setBounds(100,100,120,20);
add(lbl1);
btn1.setBounds(100,120,40,20);
add(btn1);
btn1.addActionListener(this);
}
public void actionPerformed(ActionEvent ae)
{
String num1=txt1.getText();
int i;
int k=0;
int num;
String str1="Prime no.";
String str2="Not Prime no.";
num=Integer.parseInt(num1);
for(i=1;i<=num;i++)
{
if(num%i==0)
{
k++;
}
}
if(ae.getSource()==btn1)
{
if(k==2)
{
txt2.setText(str1);
}

else
{
txt2.setText(str2);
}
}
}
}