一个窗口，用户输入三个数，你判断能否构成三角形以及面积

package triangle1;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import javax.swing.*;

import javax.swing.event.*;

public class triangle1 {

    JFrame frame1 = new JFrame("three sides");

    JFrame frame2 = new JFrame("the area");

    JFrame frame3 = new JFrame("error information");

    JLabel label1 = new JLabel("Please input three sides of the triangle:");

    JLabel label2 = new JLabel();

    JLabel label3 = new JLabel("error occurring!");

    JTextField textfield1 = new JTextField(7);

    JTextField textfield2 = new JTextField(7);

    JTextField textfield3 = new JTextField(7);

    JButton button1 = new JButton("OK");

    JButton button2 = new JButton("OK");

    JButton button3 = new JButton("OK");

    public triangle1() {

        frame1.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        frame1.getContentPane().setLayout(new java.awt.FlowLayout());

        frame2.getContentPane().setLayout(new java.awt.FlowLayout());

        frame3.getContentPane().setLayout(new java.awt.FlowLayout());

        button1.addActionListener((ActionListener) new ActionListener() {

            public void actionPerformed(ActionEvent e) {

                if (!textfield1.getText().equals("") && !textfield2.getText().equals("") && !textfield3.getText().equals("")) {

                    double a = Double.parseDouble(textfield1.getText());

                    double b = Double.parseDouble(textfield2.getText());

                    double c = Double.parseDouble(textfield3.getText());

                    if ((a + b) > c && (b + c) > a && (c + a) > b) {

                        double s = (a + b + c) / 2;

                        double area = s * (s - a) * (s - b) * (s - c);

                        label2.setText("The area of the triangle is" + area);

                        frame2.show();

                    } else {

                        frame3.show();

                    }

                } else {

                    frame3.show();

                }

            }

        });

        button2.addActionListener(new ActionListener() {

            public void actionPerformed(ActionEvent e) {

                frame2.dispose();

            }

        });

        button3.addActionListener(new ActionListener() {

            public void actionPerformed(ActionEvent e) {

                frame3.dispose();

            }

        });

        frame1.getContentPane().add(label1);

        frame1.getContentPane().add(textfield1);

        frame1.getContentPane().add(textfield2);

        frame1.getContentPane().add(textfield3);

        frame1.getContentPane().add(button1);

        frame2.getContentPane().add(label2);

        frame2.getContentPane().add(button2);

        frame3.getContentPane().add(label3);

        frame3.getContentPane().add(button3);

        frame1.setSize(400, 200);

        frame2.setSize(400, 200);

        frame3.setSize(400, 200);

    }

    public static void main(String[] args) {

        triangle1 triangle11 = new triangle1();

        triangle11.show();

    }

    private void show() {

        frame1.show();

    }

}