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import javax.swing.JFrame;
import javax.swing.Action;
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JPanel;
import java.awt.GridLayout;
import javax.swing.JOptionPane;
import java.awt.TextField;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;

public class Calcolatrice extends JFrame{

    private JButton[] numeri = new JButton[12];
    private JButton[] operatori = new JButton[4];
    private TextField casellaDiCalcolo = new TextField();
     private String stampa = "";


    public Calcolatrice(){
        setVisible(true);
        setSize(500,500);
        setLayout(new GridLayout(3,1));
        add(casellaDiCalcolo);
        add(new TabNumeri());
        add(new TabOperatori());
        addMouseListener(new AscoltatoreMouse());
        setDefaultCloseOperation(EXIT_ON_CLOSE);
    }//Calcolatrice


   class AscoltatoreMouse extends MouseAdapter{
    private double op1 = 0;
    private double op2 = 0;
    private boolean isOp2 = false;
    private String operatore = "+";

        public void mousePressed(MouseEvent e){
        JButton bottoneMagico;
            if(e.getComponent() instanceof JButton) {
        bottoneMagico = (JButton)e.getComponent();
        if(Character.isDigit(bottoneMagico.getText().charAt(0)))
            casellaDiCalcolo.setText(casellaDiCalcolo.getText()+bottoneMagico.getText());
            else {
            operatore = bottoneMagico.getText();

            if(isOp2) {
                op2 = Double.parseDouble(casellaDiCalcolo.getText());
            } else {
                op1 = Double.parseDouble(casellaDiCalcolo.getText());
            }

            casellaDiCalcolo.setText("");
            isOp2 = !isOp2;

            if(bottoneMagico.getText() == "=") {
                if(operatore == "+") casellaDiCalcolo.setText(""+(op1 + op2));
                if(operatore == "-") casellaDiCalcolo.setText(""+(op1 - op2));
                if(operatore == "*") casellaDiCalcolo.setText(""+(op1 * op2));
                if(operatore == "/") casellaDiCalcolo.setText(""+(op1 / op2));
            }
        }
        }//if
        }//mousePressed
    }//AscoltatoreMouse


    class TabNumeri extends JPanel{
        public TabNumeri(){
            setLayout(new GridLayout(4,3));
            for(int i=9;i>-1;i--){
                numeri[i] = new JButton(""+i);
                add(numeri[i]);
            }//for
            numeri[10] = new JButton("=");
            add(numeri[10]);
            numeri[11] = new JButton(".");
            add(numeri[11]);
        }//TabNumeri
    }//TabNumeri

    class TabOperatori extends JPanel{
        public TabOperatori(){
            setLayout(new GridLayout(1,4));
            operatori[0] = new JButton("/");
            add(operatori[0]);
            operatori[1] = new JButton("*");
            add(operatori[1]);
            operatori[2] = new JButton("-");
            add(operatori[2]);
            operatori[3] = new JButton("+");
            add(operatori[3]);
        }//TabOperatori
    }//TabOperatori

}//Calcolatrice