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package calculadora;

import java.awt.BorderLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;


/**
 *
 * @author Usuario
 */
public class Calculator {

    /**
     * @param args the command line argumentsk
     */
    public static void main(String[] args) {
        // TODO code application logic here
       CalculatorFrame frame = new CalculatorFrame();  
       frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
       frame.setVisible(true);
       
    }
    class CalculatorFrame extends JFrame
    {
        public CalculatorFrame()
        { 
            setTitle("Calculadora");
            CalculatorPanel panel= new CalculatorPanel();
            add(panel);
            pack();
           
        }   
    }
    class CalculatorPanel extends JPanel{
        public CalculatorPanel(){
            setLayout(new BorderLayout());
            result=0;
            lastCommand = "=";
            start=true;
            
            display = new JButton("0");
            display.setEnabled(false);
            add(display, BorderLayout.NORTH);
            
            ActionListener insert = new InserAction();
            ActionListener command = new CommandAction();
            
            panel = new JPanel();
            panel.setLayout(new GridLayout(4, 4));
            addButton("7", insert);
            addButton("8", insert);
            addButton("9", insert);
            addButton("/", command);
            
            addButton("4", insert);
            addButton("5", insert);
            addButton("6", insert);
            addButton("*", command);
            
            addButton("1", insert);
            addButton("2", insert);
            addButton("3", insert);
            addButton("-", command);
        
            addButton("0", insert);
            addButton(".", insert);
            addButton("=", command);
            addButton("+", command);
            
            add(panel, BorderLayout.CENTER);
        }
    }
    private void addButton(String label , ActionListener listener)
    {
        JButton button= new JButton(label);
        button.addActionListener(listener);
        panel.add(button);
    }    
    private class InserAction implements ActionListener{
            public void actionPerformed (ActionEvent event){
                String input = event.getActionCommand();
                if(start)
                {
                    display.setText(" ");
                    start=false;
                }
                display.setText(display.getText()+ input);
            }
    }
    private class CommandAction implements ActionListener{
        public void actionPerformed(ActionEvent event){
            String command = event.getActionCommand();
            if(start)
            {
                if (command.equals("-"))
                {
                    display.setText(command);
                    start=false;
                }  else
                 lastCommand = command;
                       
            }else
            {
                calculate(Double.parseDouble(display.getText()));
                lastCommand = command;
                start=true;
            }
        }
    }
      public void calculate (double x)
      {
       if(lastCommand.equals("+"))result+= x;
       else if(lastCommand.equals("+"))result+= x;
       else if(lastCommand.equals("+"))result+= x;
       else if(lastCommand.equals("+"))result+= x;
       else if(lastCommand.equals("+"))result+= x;
            display.setText(""+result);
      }
                    
    
      private JButton display;
      private JPanel panel;
      private double result;
      private String lastCommand;
      private boolean start;    
}