Java Calculator Using Applet

Java(Calculator Using Applet)

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

public class calc extends Applet implements ActionListener
{
 String cmd[]={"+","-","*","/","=","c"};
 int pv=0;
 String op="";
 Button b[]=new Button[16];
 TextField t1=new TextField(10);

 public void init()
 {
  setLayout(new BorderLayout());
  add(t1,"North");
  t1.setText("0");
  Panel p=new Panel();
  p.setLayout(new GridLayout(4,4));
  for(int i=0;i<16;i++)
  {
   if(i<10)
     b[i]=new Button(String.valueOf(i));
   else
     b[i]=new Button(cmd[i%10]);
   b[i].setFont(new Font("Arial",Font.BOLD,25));
   p.add(b[i]);
   add(p,"Center");
   b[i].addActionListener(this);
  }
 }

public void actionPerformed(ActionEvent ae)
{
 int res=0;
 String cap=ae.getActionCommand();
 int cv=Integer.parseInt(t1.getText());
 if(cap.equals("c"))
 {
  t1.setText("0");
  pv=0;
  cv=0;
  res=0;
  op="";
 }
 else if(cap.equals("="))
 {
  res=0;
  if(op=="+")
    res=pv+cv;
  else if(op=="-")
    res=pv-cv;
  else if(op=="*")
    res=pv*cv;
  else if(op=="/")
    res=pv/cv;


  t1.setText(String.valueOf(res));
 }
 else if(cap.equals("+")||cap.equals("-")||cap.equals("*")||cap.equals("/"))
  {
   pv=cv;
   op=cap;
   t1.setText("0");
  }
  else
  {
   int v=cv*10+Integer.parseInt(cap);
   t1.setText(String.valueOf(v));
  }
 }
}