梯形计算

Example9_15.java


 1 public class Example9_15 {
 2     public static void main(String[] args) {
 3         WindowTriangle win=new WindowTriangle();
 4         win.setTitle("使用MVC结构");
 5         win.setBounds(100,100,420,260);
 6     }
 7 }
 8

WindowTriangle.java


 1 import java.awt.*;
 2 import java.awt.event.*;
 3 import javax.swing.*;
 4 
 5 import javax.swing.JButton;
 6 import javax.swing.JFrame;
 7 import javax.swing.JPanel;
 8 import javax.swing.JTextArea;
 9 public class WindowTriangle extends JFrame implements ActionListener{
10     Triangle triangle;
11     JTextField textA,textB,textC;
12     JTextArea showArea;
13     JButton controlButton;
14     WindowTriangle(){
15         init();
16         setVisible(true);
17         setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
18     }
19     void init() {
20         triangle=new Triangle();
21         textA=new JTextField(3);
22         textB=new JTextField(3);
23         textC=new JTextField(3);
24         showArea=new JTextArea();
25         controlButton=new JButton("计算面积");
26         JPanel pNorth=new JPanel();
27          pNorth.add(new JLabel("上底A:"));
28          pNorth.add(textA);
29          pNorth.add(new JLabel("高B:"));
30          pNorth.add(textB);
31          pNorth.add(new JLabel("下底C:"));
32          pNorth.add(textC);
33          pNorth.add(controlButton);
34          controlButton.addActionListener(this);
35         add(pNorth, BorderLayout.NORTH);
36         add(new JScrollPane(showArea),BorderLayout.CENTER);
37     }
38     public void actionPerformed(ActionEvent e) {
39         try {
40             double a=Double.parseDouble(textA.getText().trim());
41             double b=Double.parseDouble(textB.getText().trim());
42             double c=Double.parseDouble(textC.getText().trim());
43             triangle.setA(a);
44             triangle.setB(b);
45             triangle.setC(c);
46             String area=triangle.getArea();
47             showArea.append("梯形"+a+"，"+b+"，"+c+"的面积：");
48             showArea.append(area+"\n");
49         }
50         catch(Exception ex) {
51             showArea.append("\n"+ex+"\n");
52         }
53     }
54 }

Triangle.java


 1 public class Triangle {
 2      double sideA,sideB,sideC,area;
 3      boolean isTriange;
 4      public String getArea() {
 5          if(isTriange) {
 6              double p=((sideA+sideC)*sideB)/2.0;         
 7              return String.valueOf(p);
 8          }else {
 9              return "无法计算面积";
10          }
11      }
12      public void setA(double a) {
13          sideA=a;
14          if(sideA+sideC>sideC&&sideA+sideC>sideB&&sideB+sideC>sideA)
15              isTriange=true;
16          else
17              isTriange=false;
18      }
19      public void setB(double b) {
20          sideB=b;
21          if(sideA+sideC>sideC&&sideA+sideC>sideB&&sideB+sideC>sideA)
22              isTriange=true;
23          else
24              isTriange=false;
25      }
26      public void setC(double c) {
27          sideC=c;
28          if(sideA+sideC>sideC&&sideA+sideC>sideB&&sideB+sideC>sideA)
29              isTriange=true;
30          else
31              isTriange=false;
32      }
33 }

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