梯形计算

Example9_15.java

 1 public class Example9_15 {
    public static void main(String[] args) {
        WindowTriangle win=new WindowTriangle();
        win.setTitle("使用MVC结构");
        win.setBounds(100,100,420,260);
    }
}

WindowTriangle.java

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

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextArea;
public class WindowTriangle extends JFrame implements ActionListener{
    Triangle triangle;
    JTextField textA,textB,textC;
    JTextArea showArea;
    JButton controlButton;
    WindowTriangle(){
        init();
        setVisible(true);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
    void init() {
        triangle=new Triangle();
        textA=new JTextField(3);
        textB=new JTextField(3);
        textC=new JTextField(3);
        showArea=new JTextArea();
        controlButton=new JButton("计算面积");
        JPanel pNorth=new JPanel();
         pNorth.add(new JLabel("上底A:"));
         pNorth.add(textA);
         pNorth.add(new JLabel("高B:"));
         pNorth.add(textB);
         pNorth.add(new JLabel("下底C:"));
         pNorth.add(textC);
         pNorth.add(controlButton);
         controlButton.addActionListener(this);
        add(pNorth, BorderLayout.NORTH);
        add(new JScrollPane(showArea),BorderLayout.CENTER);
    }
    public void actionPerformed(ActionEvent e) {
        try {
            double a=Double.parseDouble(textA.getText().trim());
            double b=Double.parseDouble(textB.getText().trim());
            double c=Double.parseDouble(textC.getText().trim());
            triangle.setA(a);
            triangle.setB(b);
            triangle.setC(c);
            String area=triangle.getArea();
            showArea.append("梯形"+a+"，"+b+"，"+c+"的面积：");
            showArea.append(area+"
");
        }
        catch(Exception ex) {
            showArea.append("
"+ex+"
");
        }
    }
}

Triangle.java

 1 public class Triangle {
     double sideA,sideB,sideC,area;
     boolean isTriange;
     public String getArea() {
         if(isTriange) {
             double p=((sideA+sideC)*sideB)/2.0;         
             return String.valueOf(p);
         }else {
             return "无法计算面积";
         }
     }
     public void setA(double a) {
         sideA=a;
         if(sideA+sideC>sideC&&sideA+sideC>sideB&&sideB+sideC>sideA)
             isTriange=true;
         else
             isTriange=false;
     }
     public void setB(double b) {
         sideB=b;
         if(sideA+sideC>sideC&&sideA+sideC>sideB&&sideB+sideC>sideA)
             isTriange=true;
         else
             isTriange=false;
     }
     public void setC(double c) {
         sideC=c;
         if(sideA+sideC>sideC&&sideA+sideC>sideB&&sideB+sideC>sideA)
             isTriange=true;
         else
             isTriange=false;
     }
}