Java - Applet - Simple Calculator

Simple calculator applet that performs basic arithmetic operations:

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

public class SimpleCalculator extends Applet implements ActionListener {
   TextField t1, t2, t3;
   Button b1, b2, b3, b4;
   
   public void init() {
      t1 = new TextField(10);
      t2 = new TextField(10);
      t3 = new TextField(10);
      
      b1 = new Button("+");
      b2 = new Button("-");
      b3 = new Button("*");
      b4 = new Button("/");
      
      add(t1);
      add(t2);
      add(t3);
      add(b1);
      add(b2);
      add(b3);
      add(b4);
      
      b1.addActionListener(this);
      b2.addActionListener(this);
      b3.addActionListener(this);
      b4.addActionListener(this);
   }
   
   public void actionPerformed(ActionEvent ae) {
      String s1 = t1.getText();
      String s2 = t2.getText();
      
      double a = Double.parseDouble(s1);
      double b = Double.parseDouble(s2);
      
      if (ae.getSource() == b1) {
         t3.setText(String.valueOf(a + b));
      } else if (ae.getSource() == b2) {
         t3.setText(String.valueOf(a - b));
      } else if (ae.getSource() == b3) {
         t3.setText(String.valueOf(a * b));
      } else if (ae.getSource() == b4) {
         t3.setText(String.valueOf(a / b));
      }
   }
}

In this code, the init() method initializes the GUI components, such as the text fields and buttons, and adds them to the applet. The actionPerformed() method handles the button clicks and performs the appropriate arithmetic operation based on the button that was clicked. The Double.parseDouble() method is used to convert the input strings into double values, and the String.valueOf() method is used to convert the result back into a string for display in the text field.

Note that this code is just a simple example and does not include error checking or input validation. It is important to perform proper input validation in any real-world calculator application to ensure that the user input is valid and prevent errors or unexpected behavior.