实用 Java 小程序代码，助你提高编程技能265

Java 是一种功能强大的编程语言，广泛应用于从桌面应用程序到移动应用等各种领域。掌握 Java 小程序代码对于初学者和经验丰富的程序员来说都至关重要，因为它可以帮助你练习基本语法、解决问题并构建实际项目。

Java HelloWorld 程序

最简单的 Java 小程序就是经典的 "HelloWorld" 程序。它会打印出 "Hello World" 消息，让你了解 Java 的基本结构。
public class HelloWorld {
public static void main(String[] args) {
("Hello World");
}
}

计算器小程序

一个简单的计算器小程序可以帮助你练习基本的数学运算和用户交互。
import ;
public class Calculator {
public static void main(String[] args) {
Scanner input = new Scanner();
("Enter the first number: ");
int num1 = ();
("Enter the second number: ");
int num2 = ();
("Select an operation (+, -, *, /): ");
char operator = ().charAt(0);
int result;
switch (operator) {
case '+':
result = num1 + num2;
break;
case '-':
result = num1 - num2;
break;
case '*':
result = num1 * num2;
break;
case '/':
result = num1 / num2;
break;
default:
result = 0;
}
("Result: " + result);
}
}

学生成绩管理小程序

一个学生成绩管理小程序可以让你练习面向对象编程、数据库操作和用户界面设计。
import ;
public class StudentManager {
private ArrayList students = new ArrayList();
public static void main(String[] args) {
StudentManager studentManager = new StudentManager();
("John Doe", 90);
("Jane Smith", 85);
();
}
public void addStudent(String name, int score) {
(new Student(name, score));
}
public void printStudents() {
for (Student student : students) {
(() + " - " + ());
}
}
}

贪吃蛇游戏小程序

一个贪吃蛇游戏小程序可以让你练习图形编程、事件处理和算法设计。
import .*;
import .*;
import ;
import ;
public class SnakeGame extends JPanel implements KeyListener {
// 游戏设置
private final int BOARD_WIDTH = 400;
private final int BOARD_HEIGHT = 400;
private final int DOT_SIZE = 10;
private final int DELAY = 100;
// 游戏状态
private boolean isRunning;
private int[] snakeX;
private int[] snakeY;
private int snakeLength;
private int foodX;
private int foodY;
private int direction;
public SnakeGame() {
addKeyListener(this);
setFocusable(true);
setFocusTraversalKeysEnabled(false);
initGame();
}
// 初始化游戏
private void initGame() {
isRunning = false;
snakeX = new int[BOARD_WIDTH / DOT_SIZE];
snakeY = new int[BOARD_HEIGHT / DOT_SIZE];
snakeLength = 3;
resetFood();
direction = KeyEvent.VK_RIGHT;
}
// 重置食物
private void resetFood() {
foodX = (int) (() * (BOARD_WIDTH / DOT_SIZE));
foodY = (int) (() * (BOARD_HEIGHT / DOT_SIZE));
}
// 游戏循环
public void run() {
while (isRunning) {
try {
(DELAY);
} catch (InterruptedException e) {
();
}
moveSnake();
checkCollisions();
repaint();
}
}
// 移动蛇
private void moveSnake() {
for (int i = snakeLength; i > 0; i--) {
snakeX[i] = snakeX[i - 1];
snakeY[i] = snakeY[i - 1];
}
switch (direction) {
case KeyEvent.VK_UP:
snakeY[0]--;
break;
case KeyEvent.VK_DOWN:
snakeY[0]++;
break;
case KeyEvent.VK_LEFT:
snakeX[0]--;
break;
case KeyEvent.VK_RIGHT:
snakeX[0]++;
break;
}
}
// 判断碰撞
private void checkCollisions() {
// 撞到自身
for (int i = 1; i < snakeLength; i++) {
if (snakeX[0] == snakeX[i] && snakeY[0] == snakeY[i]) {
isRunning = false;
}
}
// 撞到边界
if (snakeX[0] < 0 || snakeX[0] >= BOARD_WIDTH / DOT_SIZE ||
snakeY[0] < 0 || snakeY[0] >= BOARD_HEIGHT / DOT_SIZE) {
isRunning = false;
}
// 吃到食物
if (snakeX[0] == foodX && snakeY[0] == foodY) {
snakeLength++;
resetFood();
}
}
// 绘制游戏画面
@Override
public void paint(Graphics g) {
(g);
// 绘制食物
();
(foodX * DOT_SIZE, foodY * DOT_SIZE, DOT_SIZE, DOT_SIZE);
// 绘制蛇
();
for (int i = 0; i < snakeLength; i++) {
(snakeX[i] * DOT_SIZE, snakeY[i] * DOT_SIZE, DOT_SIZE, DOT_SIZE);
}
}
// 键盘事件监听器
@Override
public void keyPressed(KeyEvent e) {
int key = ();
if (isRunning) {
switch (key) {
case KeyEvent.VK_UP:
if (direction != KeyEvent.VK_DOWN) {
direction = key;
}
break;
case KeyEvent.VK_DOWN:
if (direction != KeyEvent.VK_UP) {
direction = key;
}
break;
case KeyEvent.VK_LEFT:
if (direction != KeyEvent.VK_RIGHT) {
direction = key;
}
break;
case KeyEvent.VK_RIGHT:
if (direction != KeyEvent.VK_LEFT) {
direction = key;
}
break;
}
} else {
if (key == KeyEvent.VK_SPACE) {
initGame();
isRunning = true;
run();
}
}
}
@Override
public void keyReleased(KeyEvent e) {
}
@Override
public void keyTyped(KeyEvent e) {
}
public static void main(String[] args) {
JFrame frame = new JFrame("Snake Game");
(WindowConstants.EXIT_ON_CLOSE);
(false);
(new SnakeGame());
();
(true);
}
}

TextBox 数据验证小程序

一个 TextBox 数据验证小程序可以帮助你练习正则表达式和用户界面设计。
import .*;
import ;
import ;
public class TextBoxValidator extends JFrame {
private JPanel panel;
private JTextField textField;
private JLabel label;
private JButton button;
public TextBoxValidator() {
super("TextBox Validator");
panel = new JPanel();
(new BoxLayout(panel, BoxLayout.Y_AXIS));
textField = new JTextField(20);
label = new JLabel("Enter

2024-10-12

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