控制台程序。
语义事件与程序GUI上的组件操作有关。例如，如果选择菜单项或单击按钮，就会生成语义事件。
对组件执行操作时，例如选择菜单项或单击按钮，就会生成ActionEvent事件。在选择或取消选择某个组件时，会生成ItemEvent事件。在调整可调整的对象(如滚动条）时，就生成AdjustmentEvent事件。
上面的每一种语义事件类型都定义了相应的监听器接口，这些接口都只声明了一个方法：
1、ActionListener定义了actionPerformed(ActionEvent e)方法。
2、ItemListener定义了itemStateChanged(ItemEvent e)方法。
3、AdjustmentListener定义了adjustmentValueChanged(AdjustmentEvent e)方法。
// Applet to generate lottery entries
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.util.Random; // For random number generator @SuppressWarnings("serial")
public class Lottery extends JApplet {
// Generate NUMBER_COUNT random selections from the VALUES array
private static int[] getNumbers() {
int[] numbers = new int[NUMBER_COUNT]; // Store for the numbers to be returned
int candidate = 0; // Stores a candidate selection
for(int i = 0; i < NUMBER_COUNT; ++i) { // Loop to find the selections search:
// Loop to find a new selection different from any found so far
while(true) {
candidate = VALUES[choice.nextInt(VALUES.length)];
for(int j = 0 ; j < i ; ++j) { // Check against existing selections
if(candidate==numbers[j]) { // If it is the same
continue search; // get another random selection
}
}
numbers[i] = candidate; // Store the selection in numbers array
break; // and go to find the next
}
}
return numbers; // Return the selections
} // Initialize the applet
@Override
public void init() {
SwingUtilities.invokeLater( // Create interface components
new Runnable() { // on the event dispatching thread
public void run() {
createGUI();
}
});
} // Create User Interface for applet
public void createGUI() {
// Set up the selection buttons
Container content = getContentPane();
content.setLayout(new GridLayout(0,1)); // Set the layout for the applet // Set up the panel to hold the lucky number buttons
JPanel buttonPane = new JPanel(); // Add the pane containing numbers // Let's have a fancy panel border
buttonPane.setBorder(BorderFactory.createTitledBorder(
BorderFactory.createEtchedBorder(Color.cyan,
Color.blue),
"Every One a Winner!")); int[] choices = getNumbers(); // Get initial set of numbers
for(int i = 0 ; i < NUMBER_COUNT ; ++i) {
luckyNumbers[i] = new Selection(choices[i]);
luckyNumbers[i].addActionListener(luckyNumbers[i]); // Button is it's own listener
buttonPane.add(luckyNumbers[i]);
}
content.add(buttonPane); // Add the pane containing control buttons
JPanel controlPane = new JPanel(new FlowLayout(FlowLayout.CENTER, 5, 10)); // Add the two control buttons
JButton button; // A button variable
Dimension buttonSize = new Dimension(100,20); // Button size controlPane.add(button = new JButton("Lucky Numbers!"));
button.setBorder(BorderFactory.createRaisedBevelBorder());
button.addActionListener(new HandleControlButton(PICK_LUCKY_NUMBERS));
button.setPreferredSize(buttonSize); controlPane.add(button = new JButton("Color"));
button.setBorder(BorderFactory.createRaisedBevelBorder());
button.addActionListener(new HandleControlButton(COLOR));
button.setPreferredSize(buttonSize); content.add(controlPane);
} // Class defining custom buttons showing lottery selection
private class Selection extends JButton implements ActionListener {
// Constructor
public Selection(int value) {
super(Integer.toString(value)); // Call base constructor and set the label
this.value = value; // Save the value
setBackground(startColor);
setBorder(BorderFactory.createRaisedBevelBorder()); // Add button border
setPreferredSize(new Dimension(80,20));
} // Handle selection button event
public void actionPerformed(ActionEvent e) {
// Change this selection to a new selection
int candidate = 0;
while(true) { // Loop to find a different selection
candidate = VALUES[choice.nextInt(VALUES.length)];
if(!isCurrentSelection(candidate)) { // If it is different
break; // end the loop
}
}
setValue(candidate); // We have one so set the button value
}
// Set the value for the selection
public void setValue(int value) {
setText(Integer.toString(value)); // Set value as the button label
this.value = value; // Save the value
} // Check the value for the selection
boolean hasValue(int possible) {
return value==possible; // Return true if equals current value
} // Check the current choices
boolean isCurrentSelection(int possible) {
for(int i = 0 ; i < NUMBER_COUNT ; ++i) { // For each button
if(luckyNumbers[i].hasValue(possible)) { // check against possible
return true; // Return true for any =
}
}
return false; // Otherwise return false
} private int value; // Value for the selection button
} // Class defining a handler for a control button
private class HandleControlButton implements ActionListener {
// Constructor
public HandleControlButton(int buttonID) {
this.buttonID = buttonID; // Store the button ID
} // Handle button click
public void actionPerformed(ActionEvent e) {
switch(buttonID) {
case PICK_LUCKY_NUMBERS:
int[] numbers = getNumbers(); // Get maxCount random numbers
for(int i = 0; i < NUMBER_COUNT; ++i) {
luckyNumbers[i].setValue(numbers[i]); // Set the button VALUES
}
break;
case COLOR:
Color color = new Color(
flipColor.getRGB()^luckyNumbers[0].getBackground().getRGB());
for(int i = 0; i < NUMBER_COUNT; ++i)
luckyNumbers[i].setBackground(color); // Set the button colors
break;
}
} private int buttonID;
} final static int NUMBER_COUNT = 6; // Number of lucky numbers
final static int MIN_VALUE = 1; // Minimum in range
final static int MAX_VALUE = 49; // Maximum in range
final static int[] VALUES = new int[MAX_VALUE-MIN_VALUE+1]; // Array of possible VALUES
static { // Initialize array
for(int i = 0 ; i < VALUES.length ; ++i)
VALUES[i] = i + MIN_VALUE;
} // An array of custom buttons for the selected numbers
private Selection[] luckyNumbers = new Selection[NUMBER_COUNT];
final public static int PICK_LUCKY_NUMBERS = 1; // Select button ID
final public static int COLOR = 2; // Color button ID // swap colors
Color flipColor = new Color(Color.YELLOW.getRGB()^Color.RED.getRGB()); Color startColor = Color.YELLOW; // start color private static Random choice = new Random(); // Random number generator
}
还需要一个HTML文件：
<html>
<head>
</head>
<body bgcolor="000000">
<center>
<applet
code = "Lottery.class"
width = "300"
height = "200"
>
</applet>
</center>
</body>
</html>