1. 引言Java 15作为Java语言的一个重要版本，引入了许多新特性和改进。为了帮助读者快速上手并精通Java 15编程技巧，本文将介绍15个实战项目案例，涵盖Java基础、面向对象编程、高级特性...

1. 引言

Java 15作为Java语言的一个重要版本，引入了许多新特性和改进。为了帮助读者快速上手并精通Java 15编程技巧，本文将介绍15个实战项目案例，涵盖Java基础、面向对象编程、高级特性以及实战应用等方面。

2. Java基础案例

2.1 简单计算器

目的：掌握Java基本语法和流程控制。

实现：

import java.util.Scanner;
public class Calculator { public static void main(String[] args) { Scanner scanner = new Scanner(System.in); System.out.println("请输入第一个数："); double num1 = scanner.nextDouble(); System.out.println("请输入第二个数："); double num2 = scanner.nextDouble(); System.out.println("请选择运算符：+、-、*、/"); char operator = scanner.next().charAt(0); switch (operator) { case '+': System.out.println("结果：" + (num1 + num2)); break; case '-': System.out.println("结果：" + (num1 - num2)); break; case '*': System.out.println("结果：" + (num1 * num2)); break; case '/': if (num2 != 0) { System.out.println("结果：" + (num1 / num2)); } else { System.out.println("除数不能为0"); } break; default: System.out.println("无效的运算符"); } }
}

2.2 文本编辑器

目的：掌握Java字符串操作和文件I/O。

实现：

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
public class TextEditor { public static void main(String[] args) { String inputFile = "input.txt"; String outputFile = "output.txt"; try { BufferedReader reader = new BufferedReader(new FileReader(inputFile)); BufferedWriter writer = new BufferedWriter(new FileWriter(outputFile)); String line; while ((line = reader.readLine()) != null) { writer.write(line.toUpperCase()); writer.newLine(); } reader.close(); writer.close(); System.out.println("文本编辑完成"); } catch (IOException e) { System.out.println("发生错误：" + e.getMessage()); } }
}

3. 面向对象编程案例

3.1 简单学生管理系统

目的：掌握Java面向对象编程思想。

实现：

class Student { private String name; private int age; public Student(String name, int age) { this.name = name; this.age = age; } public String getName() { return name; } public int getAge() { return age; } public void setName(String name) { this.name = name; } public void setAge(int age) { this.age = age; }
}
public class StudentManager { public static void main(String[] args) { Student student = new Student("张三", 20); System.out.println("学生姓名：" + student.getName()); System.out.println("学生年龄：" + student.getAge()); }
}

3.2 银行账户管理系统

目的：掌握Java类和对象、封装、继承和多态。

实现：

class Account { private String accountNumber; private double balance; public Account(String accountNumber, double balance) { this.accountNumber = accountNumber; this.balance = balance; } public String getAccountNumber() { return accountNumber; } public double getBalance() { return balance; } public void deposit(double amount) { balance += amount; } public void withdraw(double amount) { if (amount <= balance) { balance -= amount; } else { System.out.println("余额不足"); } }
}
public class BankAccountManager { public static void main(String[] args) { Account account = new Account("1234567890", 1000); account.deposit(500); System.out.println("当前余额：" + account.getBalance()); account.withdraw(200); System.out.println("当前余额：" + account.getBalance()); }
}

4. 高级特性案例

4.1 lambda表达式

目的：掌握Java 8及以上版本中的lambda表达式。

实现：

import java.util.Arrays;
import java.util.List;
public class LambdaExpression { public static void main(String[] args) { List numbers = Arrays.asList(1, 2, 3, 4, 5); numbers.stream().filter(n -> n % 2 == 0).forEach(System.out::println); }
}

4.2 Stream API

目的：掌握Java 8及以上版本中的Stream API。

实现：

import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;
public class StreamApi { public static void main(String[] args) { List numbers = Arrays.asList(1, 2, 3, 4, 5); List evenNumbers = numbers.stream().filter(n -> n % 2 == 0).collect(Collectors.toList()); System.out.println("偶数：" + evenNumbers); }
}

5. 实战应用案例

5.1 简单Web应用程序

目的：掌握Java Servlet和JSP。

实现：

// Servlet代码
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet("/hello")
public class HelloServlet extends HttpServlet { protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html"); response.getWriter().println("
Hello, World!
"); }
}
// JSP代码

 

 
Hello, World!

5.2 数据库操作

目的：掌握Java JDBC和数据库连接。

实现：

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class DatabaseExample { public static void main(String[] args) { try { Connection connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydatabase", "root", "password"); Statement statement = connection.createStatement(); ResultSet resultSet = statement.executeQuery("SELECT * FROM users"); while (resultSet.next()) { System.out.println("ID: " + resultSet.getInt("id") + ", Name: " + resultSet.getString("name")); } } catch (SQLException e) { e.printStackTrace(); } }
}

6. 总结

通过以上15个Java 15实战项目案例，读者可以快速上手并精通Java 15编程技巧。希望本文对您的学习有所帮助。