TrianglePJ_Swing_Model

package it.cefi.view;
import java.awt.GridLayout;
import java.text.NumberFormat;
import javax.swing.BoxLayout;
import javax.swing.JButton;
import javax.swing.JFormattedTextField;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.text.NumberFormatter;

import it.cefi.model.Triangle;

@SuppressWarnings("serial")
public class Frame extends JFrame {

    public Frame() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JFrame mainFrame = new JFrame("Triangle Checker");
        mainFrame.setLayout(new BoxLayout(mainFrame.getContentPane(), BoxLayout.PAGE_AXIS));

        NumberFormat format = NumberFormat.getInstance();
        NumberFormatter formatter = new NumberFormatter(format);
        formatter.setValueClass(Double.class);
        formatter.setMinimum(Double.MIN_VALUE);
        formatter.setMaximum(Double.MAX_VALUE);
        formatter.setAllowsInvalid(false);



        JPanel upperPanel = new JPanel(new GridLayout(0, 2));
        JLabel sideA = new JLabel("Side A");
        JFormattedTextField textA = new JFormattedTextField(formatter);
        JLabel sideB = new JLabel("Side B");
        JFormattedTextField textB = new JFormattedTextField(formatter);
        JLabel sideC = new JLabel("Side C");
        JFormattedTextField textC = new JFormattedTextField(formatter);

        upperPanel.add(sideA);
        upperPanel.add(textA);
        upperPanel.add(sideB);
        upperPanel.add(textB);
        upperPanel.add(sideC);
        upperPanel.add(textC);
        mainFrame.add(upperPanel);

        JPanel lowerPanel = new JPanel();
        JButton checker = new JButton("Check!");

        lowerPanel.add(checker);
        mainFrame.add(lowerPanel);

        mainFrame.setLocationRelativeTo(null);
        mainFrame.setSize(300, 150);
        mainFrame.setResizable(false);
        mainFrame.setVisible(true);



        checker.addActionListener(e -> {

            Triangle triangle = new Triangle(   Double.parseDouble(textA.getText()),
                                                Double.parseDouble(textB.getText()),
                                                Double.parseDouble(textC.getText()));

            if (triangle.isEquilatero())
                JOptionPane.showMessageDialog(mainFrame, "E' Equilatero!");
            else if (triangle.isIsoscele())
                JOptionPane.showMessageDialog(mainFrame, "E' Isoscele!");
            else if (triangle.isScaleno())
                JOptionPane.showMessageDialog(mainFrame, "E' Scaleno!");
            else
                JOptionPane.showMessageDialog(mainFrame, "E che cos'è!?");
        });

    }

}