1
POST /api/chat HTTP/1.1
2
Host: api.example.com
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Content-Type: application/json
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Authorization: Bearer sk-xxxxx
5

6
{
7
  "message": "你好"
8
}

1
{
2
  "name": "张三",
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  "age": 25,
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  "city": "北京",
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  "hobbies": ["读书", "游泳", "编程"],
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  "address": {
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    "street": "长安街",
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    "number": 1
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  }
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}

1
// 捕获特定异常
2
try {
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    int result = 10 / 0;
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    System.out.println(result);
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} catch (ArithmeticException e) {
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    System.err.println("错误：不能除以零！");
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    System.err.println("异常信息：" + e.getMessage());
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}
9

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// 捕获多个异常
11
try {
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    int[] numbers = {1, 2, 3};
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    System.out.println(numbers[10]);  // 数组索引越界
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} catch (ArrayIndexOutOfBoundsException e) {
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    System.err.println("错误：数组索引越界！");
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} catch (Exception e) {
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    System.err.println("其他错误：" + e.getMessage());
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}

1
try {
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    // 可能会出错的代码
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    FileReader file = new FileReader("data.txt");
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    // 读取文件...
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} catch (FileNotFoundException e) {
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    System.err.println("文件不存在：" + e.getMessage());
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} finally {
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    System.out.println("finally 块总是会执行");
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}

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// 使用 throws 声明方法可能抛出异常
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public static void readFile(String filename) throws IOException {
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    FileReader file = new FileReader(filename);
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    // 读取文件...
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}
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// 使用 throw 手动抛出异常
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public static int divide(int a, int b) {
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    if (b == 0) {
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        throw new ArithmeticException("不能除以零");
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    }
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    return a / b;
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}

1
import okhttp3.*;
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import java.io.IOException;
3

4
public class HttpWithErrorHandling {
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    public static void main(String[] args) {
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        OkHttpClient client = new OkHttpClient();
7

8
        try {
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            Request request = new Request.Builder()
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                    .url("https://api.example.com/data")
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                    .build();
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            Response response = client.newCall(request).execute();
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            if (!response.isSuccessful()) {
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                throw new IOException("HTTP 错误：" + response.code());
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            }
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            String responseData = response.body().string();
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            System.out.println(responseData);
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22
        } catch (IOException e) {
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            System.err.println("请求失败：" + e.getMessage());
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        }
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    }
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}

1
public class DebugExample {
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    public static void main(String[] args) {
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        int a = 10;
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        int b = 20;
5

6
        System.out.println("输入：a=" + a + ", b=" + b);  // 调试输出
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        int result = calculate(a, b);
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        System.out.println("结果：" + result);  // 调试输出
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    }
12

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    public static int calculate(int a, int b) {
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        System.out.println("计算中...");  // 调试输出
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        return a + b;
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    }
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}

1
Exception in thread "main" java.lang.ArithmeticException: / by zero
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    at Main.main(Main.java:5)

1
// 单行注释：解释这行代码的作用
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String name = "张三";
3

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/**
5
 * 多行注释：
6
 * 用于解释复杂的功能或逻辑
7
 *
8
 * @param name 用户名
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 * @return 问候语
10
 */
11
public static String greet(String name) {
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    return "你好，" + name + "！";
13
}
14

15
// JavaDoc 注释（用于生成文档）
16
/**
17
 * 计算两个数的和
18
 *
19
 * @param a 第一个数
20
 * @param b 第二个数
21
 * @return 两个数的和
22
 * @throws ArithmeticException 如果发生算术错误
23
 */
24
public static int add(int a, int b) throws ArithmeticException {
25
    return a + b;
26
}

1
// 定义类
2
public class Person {
3
    // 属性（字段）
4
    private String name;
5
    private int age;
6

7
    // 构造方法
8
    public Person(String name, int age) {
9
        this.name = name;
10
        this.age = age;
11
    }
12

13
    // Getter 方法
14
    public String getName() {
15
        return name;
16
    }
17

18
    public int getAge() {
19
        return age;
20
    }
21

22
    // Setter 方法
23
    public void setName(String name) {
24
        this.name = name;
25
    }
26

27
    public void setAge(int age) {
28
        this.age = age;
29
    }
30

31
    // 方法
32
    public void introduce() {
33
        System.out.println("我是 " + name + "，今年 " + age + " 岁");
34
    }
35
}
36

37
// 使用类
38
public class Main {
39
    public static void main(String[] args) {
40
        // 创建对象
41
        Person person = new Person("张三", 25);
42

43
        // 调用方法
44
        person.introduce();  // 输出：我是 张三，今年 25 岁
45

46
        // 访问属性
47
        System.out.println(person.getName());  // 输出：张三
48
    }
49
}

1
// 父类
2
public class Animal {
3
    protected String name;
4

5
    public Animal(String name) {
6
        this.name = name;
7
    }
8

9
    public void eat() {
10
        System.out.println(name + " 在吃东西");
11
    }
12
}
13

14
// 子类
15
public class Dog extends Animal {
16
    private String breed;
17

18
    public Dog(String name, String breed) {
19
        super(name);
20
        this.breed = breed;
21
    }
22

23
    // 重写父类方法
24
    @Override
25
    public void eat() {
26
        System.out.println(name + "（" + breed + "）在吃狗粮");
27
    }
28

29
    // 新增方法
30
    public void bark() {
31
        System.out.println(name + " 在汪汪叫");
32
    }
33
}
34

35
// 使用继承
36
public class Main {
37
    public static void main(String[] args) {
38
        Dog dog = new Dog("旺财", "拉布拉多");
39
        dog.eat();   // 输出：旺财（拉布拉多）在吃狗粮
40
        dog.bark();  // 输出：旺财 在汪汪叫
41
    }
42
}

1
// 定义接口
2
public interface Flyable {
3
    void fly();
4
}
5

6
// 实现接口
7
public class Bird implements Flyable {
8
    private String name;
9

10
    public Bird(String name) {
11
        this.name = name;
12
    }
13

14
    @Override
15
    public void fly() {
16
        System.out.println(name + " 在飞翔");
17
    }
18
}
19

20
// 使用接口
21
public class Main {
22
    public static void main(String[] args) {
23
        Bird bird = new Bird("小鸟");
24
        bird.fly();  // 输出：小鸟 在飞翔
25
    }
26
}

1
public class Calculator {
2
    /**
3
     * 简单计算器
4
     *
5
     * @param a 第一个数字
6
     * @param b 第二个数字
7
     * @param operator 运算符（+、-、*、/）
8
     * @return 计算结果
9
     */
10
    public static double calculate(double a, double b, char operator) {
11
        switch (operator) {
12
            case '+':
13
                return a + b;
14
            case '-':
15
                return a - b;
16
            case '*':
17
                return a * b;
18
            case '/':
19
                if (b == 0) {
20
                    throw new ArithmeticException("不能除以零");
21
                }
22
                return a / b;
23
            default:
24
                throw new IllegalArgumentException("不支持的运算符：" + operator);
25
        }
26
    }
27

28
    public static void main(String[] args) {
29
        // 测试
30
        System.out.println(calculate(10, 5, '+'));  // 输出：15.0
31
        System.out.println(calculate(10, 5, '/'));  // 输出：2.0
32

33
        try {
34
            System.out.println(calculate(10, 0, '/'));
35
        } catch (ArithmeticException e) {
36
            System.err.println(e.getMessage());  // 输出：不能除以零
37
        }
38
    }
39
}

1
import java.util.HashMap;
2
import java.util.Map;
3

4
public class StudentManager {
5
    private Map<String, Map<String, Integer>> students;
6

7
    public StudentManager() {
8
        students = new HashMap<>();
9
        // 添加初始数据
10
        addStudent("张三", Map.of("语文", 85, "数学", 90, "英语", 88));
11
        addStudent("李四", Map.of("语文", 78, "数学", 95, "英语", 82));
12
        addStudent("王五", Map.of("语文", 92, "数学", 88, "英语", 90));
13
    }
14

15
    public void addStudent(String name, Map<String, Integer> scores) {
16
        students.put(name, scores);
17
    }
18

19
    public double calculateAverage(Map<String, Integer> scores) {
20
        return scores.values().stream()
21
                .mapToInt(Integer::intValue)
22
                .average()
23
                .orElse(0.0);
24
    }
25

26
    public String getStudentInfo(String name) {
27
        if (students.containsKey(name)) {
28
            Map<String, Integer> scores = students.get(name);
29
            double average = calculateAverage(scores);
30
            return String.format("%s 的成绩：%s，平均分：%.2f",
31
                    name, scores, average);
32
        } else {
33
            return "错误：找不到学生 " + name;
34
        }
35
    }
36

37
    public static void main(String[] args) {
38
        StudentManager manager = new StudentManager();
39
        System.out.println(manager.getStudentInfo("张三"));
40
        System.out.println(manager.getStudentInfo("赵六"));
41
    }
42
}

1
import okhttp3.*;
2
import java.io.IOException;
3

4
public class WeatherAPI {
5
    private static final String API_KEY = "your-api-key";
6
    private static final String BASE_URL = "https://api.openweathermap.org/data/2.5/weather";
7

8
    public static String getWeather(String city) {
9
        OkHttpClient client = new OkHttpClient();
10

11
        String url = String.format("%s?q=%s&appid=%s&units=metric&lang=zh_cn",
12
                BASE_URL, city, API_KEY);
13

14
        Request request = new Request.Builder()
15
                .url(url)
16
                .build();
17

18
        try (Response response = client.newCall(request).execute()) {
19
            if (response.isSuccessful()) {
20
                return response.body().string();
21
            } else {
22
                return "获取天气失败：HTTP " + response.code();
23
            }
24
        } catch (IOException e) {
25
            return "获取天气失败：" + e.getMessage();
26
        }
27
    }
28

29
    public static void main(String[] args) {
30
        String weather = getWeather("北京");
31
        System.out.println(weather);
32
    }
33
}