本文目录导读：
我来为您提供几个典型的Java需求案例，从基础到进阶,适合不同学习阶段。
基础案例：学生成绩管理系统
需求描述
实现一个简单的学生成绩管理系统,支持学生信息的增删改查。
实现代码
import java.util.*;
public class StudentGradeManager {
private Map<String, Student> students = new HashMap<>();
// 学生类
static class Student {
String id;
String name;
double score;
public Student(String id, String name, double score) {
this.id = id;
this.name = name;
this.score = score;
}
@Override
public String toString() {
return String.format("学号: %s, 姓名: %s, 成绩: %.1f", id, name, score);
}
}
// 添加学生
public void addStudent(String id, String name, double score) {
students.put(id, new Student(id, name, score));
System.out.println("添加成功！");
}
// 删除学生
public void removeStudent(String id) {
if (students.remove(id) != null) {
System.out.println("删除成功！");
} else {
System.out.println("未找到该学生！");
}
}
// 查找学生
public void findStudent(String id) {
Student student = students.get(id);
if (student != null) {
System.out.println(student);
} else {
System.out.println("未找到该学生！");
}
}
// 显示所有学生
public void displayAll() {
if (students.isEmpty()) {
System.out.println("暂无学生信息");
return;
}
students.values().stream()
.sorted((a,b) -> Double.compare(b.score, a.score))
.forEach(System.out::println);
}
public static void main(String[] args) {
StudentGradeManager manager = new StudentGradeManager();
Scanner scanner = new Scanner(System.in);
while (true) {
System.out.println("\n=== 学生成绩管理系统 ===");
System.out.println("1. 添加学生");
System.out.println("2. 删除学生");
System.out.println("3. 查找学生");
System.out.println("4. 显示所有学生");
System.out.println("5. 退出");
System.out.print("请选择操作: ");
int choice = scanner.nextInt();
scanner.nextLine(); // 消耗换行符
switch (choice) {
case 1:
System.out.print("请输入学号: ");
String id = scanner.nextLine();
System.out.print("请输入姓名: ");
String name = scanner.nextLine();
System.out.print("请输入成绩: ");
double score = scanner.nextDouble();
manager.addStudent(id, name, score);
break;
case 2:
System.out.print("请输入要删除的学号: ");
String delId = scanner.nextLine();
manager.removeStudent(delId);
break;
case 3:
System.out.print("请输入要查找的学号: ");
String findId = scanner.nextLine();
manager.findStudent(findId);
break;
case 4:
manager.displayAll();
break;
case 5:
System.out.println("感谢使用！");
return;
default:
System.out.println("无效选择！");
}
}
}
}
进阶案例：简易银行账户系统
需求描述
实现银行账户的存取款、转账、交易记录查询功能。
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.util.*;
// 交易记录类
class Transaction {
private String type;
private double amount;
private double balance;
private LocalDateTime time;
public Transaction(String type, double amount, double balance) {
this.type = type;
this.amount = amount;
this.balance = balance;
this.time = LocalDateTime.now();
}
@Override
public String toString() {
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
return String.format("[%s] %s: %.2f, 余额: %.2f",
time.format(formatter), type, amount, balance);
}
}
// 银行账户类
class BankAccount {
private String accountNumber;
private String holderName;
private double balance;
private List<Transaction> transactions;
private static final double MIN_BALANCE = 100.0;
public BankAccount(String accountNumber, String holderName, double initialBalance) {
this.accountNumber = accountNumber;
this.holderName = holderName;
this.balance = initialBalance;
this.transactions = new ArrayList<>();
addTransaction("开户", initialBalance);
}
public synchronized boolean deposit(double amount) {
if (amount <= 0) {
System.out.println("存款金额必须为正数！");
return false;
}
balance += amount;
addTransaction("存款", amount);
System.out.printf("存款成功！当前余额: %.2f\n", balance);
return true;
}
public synchronized boolean withdraw(double amount) {
if (amount <= 0) {
System.out.println("取款金额必须为正数！");
return false;
}
if (balance - amount < MIN_BALANCE) {
System.out.println("余额不足！需保留最低余额100元");
return false;
}
balance -= amount;
addTransaction("取款", amount);
System.out.printf("取款成功！当前余额: %.2f\n", balance);
return true;
}
public synchronized boolean transfer(BankAccount target, double amount) {
if (this.withdraw(amount)) {
target.deposit(amount);
addTransaction("转账支出", amount);
target.addTransaction("转账收入", amount);
return true;
}
return false;
}
private void addTransaction(String type, double amount) {
transactions.add(new Transaction(type, amount, balance));
}
public void showTransactionHistory() {
System.out.println("\n交易记录：");
transactions.forEach(System.out::println);
}
public String getAccountInfo() {
return String.format("账号: %s\n户主: %s\n余额: %.2f",
accountNumber, holderName, balance);
}
// Getters
public String getAccountNumber() { return accountNumber; }
public double getBalance() { return balance; }
}
// 银行系统
public class BankingSystem {
private Map<String, BankAccount> accounts = new HashMap<>();
private Scanner scanner = new Scanner(System.in);
public void createAccount() {
System.out.print("请输入账号: ");
String accountNumber = scanner.nextLine();
System.out.print("请输入户主姓名: ");
String holderName = scanner.nextLine();
System.out.print("请输入初始存款: ");
double initialBalance = scanner.nextDouble();
scanner.nextLine();
accounts.put(accountNumber, new BankAccount(accountNumber, holderName, initialBalance));
System.out.println("开户成功！");
}
public void run() {
while (true) {
System.out.println("\n=== 银行账户系统 ===");
System.out.println("1. 开户");
System.out.println("2. 存款");
System.out.println("3. 取款");
System.out.println("4. 转账");
System.out.println("5. 查询交易记录");
System.out.println("6. 查看账户信息");
System.out.println("7. 退出");
System.out.print("请选择: ");
int choice = scanner.nextInt();
scanner.nextLine();
switch (choice) {
case 1:
createAccount();
break;
case 2:
// 存款操作
break;
case 7:
System.out.println("感谢使用！");
return;
default:
System.out.println("无效选择！");
}
}
}
public static void main(String[] args) {
new BankingSystem().run();
}
}
实用工具案例：文件批处理工具
需求描述
实现批量重命名文件和目录统计功能。
import java.io.*;
import java.nio.file.*;
import java.util.*;
public class FileBatchProcessor {
// 批量重命名文件
public static void renameFiles(String directory, String prefix, String extension) {
File dir = new File(directory);
File[] files = dir.listFiles((d, name) -> name.endsWith(extension));
if (files == null || files.length == 0) {
System.out.println("未找到匹配的文件");
return;
}
int count = 1;
for (File file : files) {
String newName = String.format("%s_%d%s", prefix, count++, extension);
File newFile = new File(dir, newName);
if (file.renameTo(newFile)) {
System.out.printf("重命名: %s -> %s\n", file.getName(), newName);
} else {
System.out.printf("重命名失败: %s\n", file.getName());
}
}
}
// 统计目录信息
public static void directoryStats(String path) throws IOException {
Path dirPath = Paths.get(path);
if (!Files.exists(dirPath) || !Files.isDirectory(dirPath)) {
System.out.println("无效的目录路径");
return;
}
Map<String, Long> extensionCount = new HashMap<>();
long totalSize = 0;
int fileCount = 0;
int dirCount = 0;
try (DirectoryStream<Path> stream = Files.newDirectoryStream(dirPath)) {
for (Path entry : stream) {
if (Files.isDirectory(entry)) {
dirCount++;
} else {
fileCount++;
String fileName = entry.getFileName().toString();
String ext = fileName.contains(".") ?
fileName.substring(fileName.lastIndexOf(".")) : "无扩展名";
extensionCount.merge(ext, 1L, Long::sum);
totalSize += Files.size(entry);
}
}
}
System.out.println("\n=== 目录统计 ===");
System.out.printf("目录：%s\n", path);
System.out.printf("文件总数：%d\n", fileCount);
System.out.printf("子目录数：%d\n", dirCount);
System.out.printf("总大小：%.2f MB\n", totalSize / (1024.0 * 1024.0));
System.out.println("\n文件类型统计：");
extensionCount.entrySet().stream()
.sorted(Map.Entry.<String, Long>comparingByValue().reversed())
.forEach(e -> System.out.printf(" %s: %d个\n", e.getKey(), e.getValue()));
}
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
while (true) {
System.out.println("\n=== 文件批处理工具 ===");
System.out.println("1. 批量重命名文件");
System.out.println("2. 目录统计");
System.out.println("3. 退出");
System.out.print("请选择: ");
int choice = scanner.nextInt();
scanner.nextLine();
switch (choice) {
case 1:
System.out.print("请输入目录路径: ");
String dir = scanner.nextLine();
System.out.print("请输入文件前缀: ");
String prefix = scanner.nextLine();
System.out.print("请输入文件扩展名(如.txt): ");
String ext = scanner.nextLine();
renameFiles(dir, prefix, ext);
break;
case 2:
System.out.print("请输入目录路径: ");
String path = scanner.nextLine();
try {
directoryStats(path);
} catch (IOException e) {
System.out.println("处理出错: " + e.getMessage());
}
break;
case 3:
System.out.println("感谢使用！");
return;
default:
System.out.println("无效选择！");
}
}
}
}
设计模式案例：简易订单系统
需求描述
使用工厂模式和观察者模式实现订单处理系统。
import java.util.*;
// 1. 工厂模式 - 创建不同类型的订单
interface Order {
void process();
double calculateTotal();
}
class PhysicalOrder implements Order {
private double amount;
private double shippingCost;
public PhysicalOrder(double amount, double shippingCost) {
this.amount = amount;
this.shippingCost = shippingCost;
}
@Override
public void process() {
System.out.println("处理实物订单：准备发货");
}
@Override
public double calculateTotal() {
return amount + shippingCost;
}
}
class DigitalOrder implements Order {
private double amount;
private String downloadLink;
public DigitalOrder(double amount, String downloadLink) {
this.amount = amount;
this.downloadLink = downloadLink;
}
@Override
public void process() {
System.out.println("处理数字订单：发送下载链接 " + downloadLink);
}
@Override
public double calculateTotal() {
return amount; // 数字产品免运费
}
}
// 2. 观察者模式 - 订单通知
interface OrderObserver {
void onOrderCreated(Order order);
void onOrderProcessed(Order order);
}
class EmailNotifier implements OrderObserver {
@Override
public void onOrderCreated(Order order) {
System.out.println("[邮件通知] 订单已创建，金额：" + order.calculateTotal());
}
@Override
public void onOrderProcessed(Order order) {
System.out.println("[邮件通知] 订单已处理完成");
}
}
class SMSNotifier implements OrderObserver {
@Override
public void onOrderCreated(Order order) {
System.out.println("[短信通知] 您有新订单！");
}
@Override
public void onOrderProcessed(Order order) {
System.out.println("[短信通知] 订单处理完成，请查收");
}
}
// 3. 订单管理器
class OrderManager {
private List<Order> orders = new ArrayList<>();
private List<OrderObserver> observers = new ArrayList<>();
public void addObserver(OrderObserver observer) {
observers.add(observer);
}
public void createOrder(Order order) {
orders.add(order);
observers.forEach(obs -> obs.onOrderCreated(order));
}
public void processAllOrders() {
for (Order order : orders) {
order.process();
observers.forEach(obs -> obs.onOrderProcessed(order));
}
}
public double getTotalRevenue() {
return orders.stream().mapToDouble(Order::calculateTotal).sum();
}
}
// 订单工厂
class OrderFactory {
public static Order createOrder(String type, double amount, String extra) {
switch (type.toLowerCase()) {
case "physical":
double shippingCost = Double.parseDouble(extra);
return new PhysicalOrder(amount, shippingCost);
case "digital":
return new DigitalOrder(amount, extra);
default:
throw new IllegalArgumentException("未知订单类型: " + type);
}
}
}
// 主测试类
public class OrderSystem {
public static void main(String[] args) {
OrderManager manager = new OrderManager();
// 注册观察者
manager.addObserver(new EmailNotifier());
manager.addObserver(new SMSNotifier());
// 创建订单
Order physicalOrder = OrderFactory.createOrder("physical", 299.99, "25.00");
Order digitalOrder = OrderFactory.createOrder("digital", 99.99, "https://download.example.com/product");
manager.createOrder(physicalOrder);
manager.createOrder(digitalOrder);
System.out.println("\n=== 处理所有订单 ===");
manager.processAllOrders();
System.out.printf("\n总收入: %.2f\n", manager.getTotalRevenue());
}
}
学习建议
- 基础案例：掌握Java基础语法、集合框架、面向对象编程
- 进阶案例：学习多线程、IO操作、异常处理
- 实用工具：练习文件操作、正则表达式、日期处理
- 设计模式：理解常见设计模式的应用场景
这些案例涵盖了Java开发中常用的技术和设计模式,建议按照从简到繁的顺序逐步学习实践。
