Java入门【01】运行Java程序

使用的教材：Java核心技术

Java核心技术第一章主要讲述Java的特性以及Java的发展史

第二章搭建开发环境，由于书比较老，对于现在也不是很适合，需要安装可以去百度搜索搭建Java环境的方法，现在的计算机越来越强大，环境目录都基本不用配置，应该说是傻瓜式操作。

然后就是介绍使用命令行和集成开发环境的使用，并给出代码运行。

命令行窗口并不能引起人的兴奋。所以又给出一个图形化应用程序—–图片查看器。

代码如下：

 1 import javax.swing.*;
 2 import java.awt.*;
 3 import java.awt.event.ActionEvent;
 4 import java.awt.event.ActionListener;
 5 import java.io.File;
 6  
 7 public class ImageViewer {
 8     public static void main(String[] args) {
 9         EventQueue.invokeLater(new Runnable() {
10             @Override
11             public void run() {
12                 JFrame frame = new ImageViewerFrame();
13                 frame.setTitle("ImageViewer");
14                 frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
15                 frame.setVisible(true);
16             }
17         });
18     }
19 }
20 class ImageViewerFrame extends JFrame{
21     private JLabel label;
22     private JFileChooser chooser;
23     private static final int DEFAULT_WIDTH = 300;
24     private static final int DEFAULT_HEIGHT = 400;
25  
26     public ImageViewerFrame() throws HeadlessException {
27         setSize(DEFAULT_WIDTH,DEFAULT_WIDTH);
28         //use a lable to display the images
29         label = new JLabel();
30         add(label);
31  
32         //set up the file chooser
33         chooser = new JFileChooser();
34         chooser.setCurrentDirectory(new File("."));
35  
36         //set up the menu bar
37         JMenuBar menuBar = new JMenuBar();
38         setJMenuBar(menuBar);
39  
40         JMenu menu = new JMenu("File");
41         menuBar.add(menu);
42  
43         JMenuItem openItem = new JMenuItem("open");
44         menu.add(openItem);
45  
46         openItem.addActionListener(new ActionListener() {
47             @Override
48             public void actionPerformed(ActionEvent actionEvent) {
49                 //show file chooser dialog
50                 int result = chooser.showOpenDialog(null);
51  
52                 //if file selected,set it as icon of the label
53                 if (result == JFileChooser.APPROVE_OPTION){
54                     String name = chooser.getSelectedFile().getPath();
55  
56                     label.setIcon(new ImageIcon(name));
57                 }
58             }
59         });
60         JMenuItem exitItem = new JMenuItem("Exit");
61         menu.add(exitItem);
62         exitItem.addActionListener(new ActionListener() {
63             @Override
64             public void actionPerformed(ActionEvent actionEvent) {
65                 System.exit(0);
66             }
67         });
68  
69     }
70 }

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代码看不懂无所谓，先敲上去，运行之后，感受一番，相信会有更大的动力。

然后还演示了Applet的使用，很遗憾，这个API已经被淘汰掉了

还是把代码放上来：WelcomeApplet.java

 1  
 2 import java.awt.*;
 3 import java.awt.event.*;
 4 import java.net.*;
 5 import javax.swing.*;
 6  
 7 public class WelcomeApplet extends JApplet{
 8     public void init(){
 9         EventQueue.invokeLater(new Runnable() {
10             @Override
11             public void run() {
12                 setLayout(new BorderLayout());
13                 JLabel label = new JLabel(getParameter("geeting"),SwingConstants.CENTER);
14                 label.setFont(new Font("Serif",Font.BOLD,18));
15                 add(label,BorderLayout.CENTER);
16                 JPanel panel = new JPanel();
17  
18                 JButton cayButton = new JButton("Cay Horstman");
19                 cayButton.addActionListener(makeAction("http://horstman.com"));
20                 panel.add(cayButton);
21  
22                 JButton garyButton = new JButton("Gray Cornell");
23                 garyButton.addActionListener(makeAction("mailto:gray_cornell@apress.com"));
24                 panel.add(garyButton);
25  
26                 add(panel,BorderLayout.SOUTH);
27             }
28         });
29     }
30     private ActionListener makeAction(final String urlString){
31         return new ActionListener() {
32             @Override
33             public void actionPerformed(ActionEvent actionEvent) {
34                 try {
35                     getAppletContext().showDocument(new URL(urlString));
36                 }catch (MalformedURLException e){
37                     e.printStackTrace();
38                 }
39             }
40         };
41     }
42 }

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WelcomeApplet.html

 1 <html>
 2 <head>
 3     <meta charset="UTF-8">
 4     <title>WelcomeApplet</title>
 5 </head>
 6 <body>
 7     <hr/>
 8     <p>
 9         This applet is from the book
10         <a href="http://www.horstman.com/corejava.html">Core Java</a>
11         by <em>Cay Horstman</em> and <em>Gary Cornel</em>
12     </p>
13     <applet code="WelcomeApplet.class" width="400" height="200">
14         <param name="greeting" value="Welcome to Core Java!">
15     </applet>
16     <hr/>
17     <p><a href="WelcomeApplet.java">The source.</a></p>
18  
19 </body>
20 </html>

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