Java 最新技术实操指南：从 Java 8 + 特性到 Spring Boot 与 Hibernate 应用实践

import java.util.Arrays;
import java.util.List;

public class LambdaExample {
    public static void main(String[] args) {
        List<String> names = Arrays.asList("Alice", "Bob", "Charlie");
        
        // Lambda表达式遍历集合
        names.forEach(name -> System.out.println("Hello, " + name));
        
        // 使用函数式接口Predicate过滤元素
        names.stream()
             .filter(name -> name.length() > 4)
             .forEach(System.out::println); // 方法引用
    }
}

interface Vehicle {
    default void start() {
        System.out.println("启动车辆");
    }
    
    static void honk() {
        System.out.println("鸣笛！");
    }
}

class Car implements Vehicle {
    // 无需实现start()方法
}

public class InterfaceExample {
    public static void main(String[] args) {
        Car car = new Car();
        car.start(); // 调用接口默认方法
        Vehicle.honk(); // 调用接口静态方法
    }
}

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class TryWithResourcesExample {
    public static void main(String[] args) {
        try (BufferedReader reader = new BufferedReader(new FileReader("data.txt"))) {
            String line;
            while ((line = reader.readLine()) != null) {
                System.out.println(line);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } // 自动关闭reader资源
    }
}

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.List;

public class NIO2Example {
    public static void main(String[] args) throws IOException {
        // 创建Path对象
        Path filePath = Paths.get("data.txt");
        
        // 读取文件所有行
        List<String> lines = Files.readAllLines(filePath);
        
        // 写入文件
        Path newPath = Paths.get("newData.txt");
        Files.write(newPath, lines);
        
        // 检查文件是否存在
        boolean exists = Files.exists(filePath);
        System.out.println("文件存在: " + exists);
    }
}

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
    <groupId>com.h2database</groupId>
    <artifactId>h2</artifactId>
    <scope>runtime</scope>
</dependency>

spring.datasource.url=jdbc:h2:mem:testdb
spring.datasource.driverClassName=org.h2.Driver
spring.datasource.username=sa
spring.datasource.password=password
spring.jpa.database-platform=org.hibernate.dialect.H2Dialect
spring.h2.console.enabled=true

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;

@Entity
public class User {
    @Id
    @GeneratedValue
    private Long id;
    private String username;
    private String email;
    
    // 构造方法、Getter/Setter省略
}

import org.springframework.data.jpa.repository.JpaRepository;

public interface UserRepository extends JpaRepository<User, Long> {
    // 自动继承CRUD方法（如save、findAll、findById等）
    User findByUsername(String username); // 自定义查询方法
}

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class UserService {
    @Autowired
    private UserRepository userRepository;
    
    public User saveUser(User user) {
        return userRepository.save(user);
    }
    
    public User getUserByUsername(String username) {
        return userRepository.findByUsername(username);
    }
}