互联网公司校招 Java 面试题总结及答案含实操示例

我将基于之前总结的面试题，结合最新技术趋势，为每个核心知识点提供实操示例。这些示例采用Spring Boot 3、Java 17等最新技术栈，并包含完整的代码实现和运行步骤。

// 项目结构
java-campus-recruitment-practice
├── src/main/java/com/interview/practice
│   ├── Application.java                // 应用启动类
│   ├── config
│   │   ├── AsyncConfig.java            // 多线程配置
│   │   └── WebMvcConfig.java           // Web配置
│   ├── controller
│   │   ├── UserController.java         // 用户管理接口
│   │   └── ThreadController.java       // 多线程演示接口
│   ├── entity
│   │   ├── User.java                   // 用户实体类
│   │   └── Result.java                 // 通用返回结果
│   ├── service
│   │   ├── UserService.java            // 用户服务接口
│   │   ├── impl
│   │   │   └── UserServiceImpl.java    // 用户服务实现
│   │   └── ThreadService.java          // 多线程服务
│   ├── repository
│   │   └── UserRepository.java         // 用户数据访问
│   └── util
│       ├── HashUtils.java              // 哈希工具类
│       └── ExceptionUtil.java          // 异常处理工具
├── src/main/resources
│   ├── application.yml                 // 应用配置
│   └── db
│       └── migration                   // 数据库迁移脚本
└── pom.xml                             // Maven依赖配置

以下是各模块的核心代码实现：

// User.java - 演示Java Bean规范和Lombok使用
package com.interview.practice.entity;

import jakarta.persistence.*;
import lombok.*;
import java.time.LocalDateTime;

@Entity
@Table(name = "users")
@Data
@Builder
@NoArgsConstructor
@AllArgsConstructor
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    
    @Column(nullable = false, unique = true)
    private String username;
    
    @Column(nullable = false)
    private String password;
    
    @Column(nullable = false)
    private String email;
    
    @Column(name = "create_time")
    private LocalDateTime createTime;
    
    @Column(name = "update_time")
    private LocalDateTime updateTime;
    
    // 演示自定义方法
    public void encryptPassword() {
        this.password = HashUtils.sha256(this.password);
    }
}

// UserRepository.java - 演示Spring Data JPA和自定义查询
package com.interview.practice.repository;

import com.interview.practice.entity.User;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.Query;
import org.springframework.data.repository.query.Param;

import java.util.Optional;

public interface UserRepository extends JpaRepository<User, Long> {
    Optional<User> findByUsername(String username);
    
    // 演示自定义SQL查询
    @Query("SELECT u FROM User u WHERE u.email = :email")
    Optional<User> findByEmail(@Param("email") String email);
}

// UserServiceImpl.java - 演示事务管理和线程安全
package com.interview.practice.service.impl;

import com.interview.practice.entity.User;
import com.interview.practice.repository.UserRepository;
import com.interview.practice.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.scheduling.annotation.Async;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import java.time.LocalDateTime;
import java.util.concurrent.CompletableFuture;

@Service
public class UserServiceImpl implements UserService {
    
    @Autowired
    private UserRepository userRepository;
    
    @Override
    @Transactional
    public User createUser(User user) {
        // 检查用户名是否已存在
        if (userRepository.findByUsername(user.getUsername()).isPresent()) {
            throw new IllegalArgumentException("用户名已存在");
        }
        
        // 加密密码
        user.encryptPassword();
        user.setCreateTime(LocalDateTime.now());
        user.setUpdateTime(LocalDateTime.now());
        
        return userRepository.save(user);
    }
    
    @Override
    @Async("asyncExecutor") // 使用自定义线程池
    public CompletableFuture<User> getUserAsync(Long id) {
        // 模拟耗时操作
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
        }
        
        return CompletableFuture.completedFuture(
            userRepository.findById(id)
                .orElseThrow(() -> new IllegalArgumentException("用户不存在"))
        );
    }
}

// AsyncConfig.java - 演示线程池配置
package com.interview.practice.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.scheduling.annotation.EnableAsync;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;

import java.util.concurrent.Executor;

@Configuration
@EnableAsync
public class AsyncConfig {
    
    @Bean(name = "asyncExecutor")
    public Executor asyncExecutor() {
        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
        executor.setCorePoolSize(5);       // 核心线程数
        executor.setMaxPoolSize(10);       // 最大线程数
        executor.setQueueCapacity(25);     // 队列容量
        executor.setThreadNamePrefix("async-thread-");
        executor.setRejectedExecutionHandler(
            new java.util.concurrent.ThreadPoolExecutor.CallerRunsPolicy()
        );
        executor.initialize();
        return executor;
    }
}

// ThreadService.java - 演示各种多线程实现方式
package com.interview.practice.service;

import org.springframework.stereotype.Service;
import java.util.concurrent.*;

@Service
public class ThreadService {
    
    // 1. 继承Thread类
    public static class MyThread extends Thread {
        @Override
        public void run() {
            System.out.println("继承Thread类: " + Thread.currentThread().getName());
        }
    }
    
    // 2. 实现Runnable接口
    public static class MyRunnable implements Runnable {
        @Override
        public void run() {
            System.out.println("实现Runnable接口: " + Thread.currentThread().getName());
        }
    }
    
    // 3. 实现Callable接口
    public static class MyCallable implements Callable<String> {
        @Override
        public String call() throws Exception {
            Thread.sleep(1000);
            return "实现Callable接口: " + Thread.currentThread().getName();
        }
    }
    
    // 演示线程池使用
    public void executeWithThreadPool() {
        ExecutorService executor = Executors.newFixedThreadPool(3);
        
        // 提交Runnable任务
        executor.submit(new MyRunnable());
        
        // 提交Callable任务
        Future<String> future = executor.submit(new MyCallable());
        try {
            System.out.println(future.get());
        } catch (InterruptedException | ExecutionException e) {
            e.printStackTrace();
        }
        
        executor.shutdown();
    }
    
    // 演示CountDownLatch
    public void demoCountDownLatch() throws InterruptedException {
        CountDownLatch latch = new CountDownLatch(3);
        
        for (int i = 0; i < 3; i++) {
            final int index = i;
            new Thread(() -> {
                System.out.println("线程" + index + "开始工作");
                try {
                    Thread.sleep(1000 + index * 500);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println("线程" + index + "完成工作");
                latch.countDown();
            }).start();
        }
        
        System.out.println("主线程等待所有子线程完成...");
        latch.await();
        System.out.println("所有子线程完成工作，主线程继续执行");
    }
}

// UserController.java - 演示RESTful API设计和异常处理
package com.interview.practice.controller;

import com.interview.practice.entity.Result;
import com.interview.practice.entity.User;
import com.interview.practice.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.concurrent.CompletableFuture;

@RestController
@RequestMapping("/api/users")
public class UserController {
    
    @Autowired
    private UserService userService;
    
    @PostMapping
    public Result<User> createUser(@RequestBody User user) {
        User createdUser = userService.createUser(user);
        return Result.success(createdUser);
    }
    
    @GetMapping("/{id}")
    public Result<User> getUser(@PathVariable Long id) {
        User user = userService.getUserAsync(id).join();
        return Result.success(user);
    }
}

// Result.java - 演示通用返回结果封装
package com.interview.practice.entity;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@AllArgsConstructor
@NoArgsConstructor
public class Result<T> {
    private int code;
    private String message;
    private T data;
    
    public static <T> Result<T> success(T data) {
        return new Result<>(200, "操作成功", data);
    }
    
    public static <T> Result<T> error(int code, String message) {
        return new Result<>(code, message, null);
    }
}

# application.yml - 应用配置示例
spring:
  application:
    name: java-interview-practice
  datasource:
    url: jdbc:mysql://localhost:3306/interview_db?useSSL=false&serverTimezone=UTC
    username: root
    password: yourpassword
    driver-class-name: com.mysql.cj.jdbc.Driver
  jpa:
    hibernate:
      ddl-auto: validate
    show-sql: true
    properties:
      hibernate:
        format_sql: true
  flyway:
    enabled: true
    baseline-on-migrate: true

server:
  port: 8080
  servlet:
    context-path: /api

# 线程池配置
async:
  executor:
    core-pool-size: 5
    max-pool-size: 10
    queue-capacity: 25

-- V1__create_user_table.sql - 数据库迁移脚本
CREATE TABLE users (
    id BIGINT AUTO_INCREMENT PRIMARY KEY,
    username VARCHAR(50) NOT NULL UNIQUE,
    password VARCHAR(100) NOT NULL,
    email VARCHAR(50) NOT NULL,
    create_time TIMESTAMP NOT NULL,
    update_time TIMESTAMP NOT NULL
);

// Application.java - 应用启动类
package com.interview.practice;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.scheduling.annotation.EnableAsync;

@SpringBootApplication
@EnableAsync
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

项目运行步骤：

1. 环境准备：

   • JDK 17+
   • Maven 3.8+
   • MySQL 8.0+

2. 数据库配置：

   • 创建数据库：CREATE DATABASE interview_db;
   • 修改application.yml中的数据库连接信息

3. 项目构建与运行：

   git clone https://github.com/your-repo/java-campus-recruitment-practice.git
   cd java-campus-recruitment-practice
   mvn clean install
   mvn spring-boot:run

4. API测试：

   • 创建用户：

     curl -X POST http://localhost:8080/api/users \
     -H "Content-Type: application/json" \
     -d '{"username":"testuser","password":"123456","email":"[email protected]"}'

   • 获取用户：

     curl http://localhost:8080/api/users/1

这个项目涵盖了Java基础、多线程、集合框架、数据库操作和Spring框架等核心知识点的实操示例。你可以根据需要扩展功能，或者针对特定知识点进行深入学习。

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资源地址： pan.quark.cn/s/14fcf913b...

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