import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

// same structure and functionality as Calculator3, but using Swing
class Calculator4 {

 public static void main(String[] args) {  
    SimpleCalculator4 calculator = new SimpleCalculator4();
  } // main
  
} // Calculator4


// --- cut here into separate files ---

class SimpleCalculator4 extends JFrame implements ActionListener{  
  
  private JPanel[] p = new JPanel[3];
  private JButton[] buttons = new JButton[5];
  private JTextField opAField = new JTextField(10);
  private JTextField opBField = new JTextField(10);
  private JTextField resultField = new JTextField(10);   

  public SimpleCalculator4() { 
  getContentPane().setLayout(new GridLayout(1,3)); // swing adaption !

    p[0] = new JPanel(new GridLayout(6,1));  // operands/result fields
    p[1] = new JPanel();		             // empty panel
    p[2] = new JPanel(new GridLayout(5,1));  // operation buttons
    
    p[0].add(new JLabel("operand A"));	     // preparing left column
    p[0].add(opAField);
    p[0].add(new JLabel("operand b"));
    p[0].add(opBField);
    p[0].add(new JLabel("result"));
    p[0].add(resultField);
    
    buttons[0] = new JButton("add");	     // preparing right column
    buttons[1] = new JButton("sub");
    buttons[2] = new JButton("mul");
    buttons[3] = new JButton("int div");
    buttons[4] = new JButton("real div");
    
    buttons[0].addActionListener(this);
    buttons[1].addActionListener(this);
    buttons[2].addActionListener(this);
    buttons[3].addActionListener(this);
    buttons[4].addActionListener(this);
    
    for(int i=0;i<5;i++) {
    	p[2].add(buttons[i]);
    }
		
    for(int i=0;i<3;i++) {		    // assigning the panels to the frame
    	getContentPane().add(p[i]); 	    // swing adaption !
    }
		
    addWindowListener(new WindowAdapter() {  // register for window closing
      public void windowClosing(WindowEvent e) {
          System.exit(0);
      } 
    });

    setTitle("  My Simple Calculator, V4 in Swing");
    setSize(300,200);
    setVisible(true);   // show();	deprecated
    
  } // SimpleCalculator4()
  

    public void actionPerformed(ActionEvent event) {
	String command = event.getActionCommand();
	int a, b;
	double db;
		
  	if (command == "add") {  
  		a = Integer.parseInt(opAField.getText());	
		b = Integer.parseInt(opBField.getText());  	
		resultField.setText((a+b)+" ");
    	} else if (command == "sub") {
     	  	a = Integer.parseInt(opAField.getText());	
		b = Integer.parseInt(opBField.getText());  	
		resultField.setText((a-b)+" "); 
	} else if (command == "mul") { 
    		a = Integer.parseInt(opAField.getText());	
		b = Integer.parseInt(opBField.getText());  	
		resultField.setText((a*b)+" "); 
	} else if (command == "int div") {
    		a = Integer.parseInt(opAField.getText());	
		b = Integer.parseInt(opBField.getText());  	
		resultField.setText((a/b)+" "); 
	} else if (command == "real div") { 
    		a = Integer.parseInt(opAField.getText());	
		db = Integer.parseInt(opBField.getText());  	
		resultField.setText((a/db)+" "); 
     	} // if
    
   } // actionPerformed
  
  
} // class SimpleCalculator4