Java异常处理：常见场景与案例

原创 Bertha 。 2024-09-24 02:15 61阅读 0赞

在Java编程中，异常处理是防止程序因意外情况而崩溃的重要机制。以下是一些常见的Java异常处理场景和案例：

1. **文件操作**：
   - 检查文件是否存在：
     ```java
     File file = new File("path/to/file.txt");
     if (!file.exists()) {
         throw new IllegalArgumentException("File does not exist.");
     }
     ```
   - 读写文件，捕获可能的IOException异常：

```java
     BufferedReader br = null;
     try {
         br = new BufferedReader(new FileReader("file.txt")));

// 读取内容
         String content = br.readLine();
         System.out.println(content);
     } catch (IOException e) {
         e.printStackTrace();  // 或者使用处理方式，如记录日志等
         if (br != null) {
             try {
                 br.close();
             } catch (IOException ex) {
                 ex.printStackTrace();
             }
         }
         throw new RuntimeException("Error reading file.", e);
     }
     finally {
         if (br != null) {
             try {
                 br.close();
             } catch (IOException ex) {
                 ex.printStackTrace();
             }
             // 确保文件关闭，即使发生异常
         }
     }
     ```

2. **网络通信**：
   - 发送HTTP请求，捕获可能的Exception：

```java
     try {
         URL url = new URL("http://example.com");
         HttpURLConnection connection = (HttpURLConnection) url.openConnection();
         connection.setRequestMethod("GET");

int responseCode = connection.getResponseCode();
         if (responseCode == 200) {
             // 请求成功，读取响应内容
             BufferedReader br = new BufferedReader(new InputStreamReader(connection.getInputStream()))));
             String content = br.readLine();
             System.out.println(content);
         } else {
             // 请求失败或状态码不为200
             System.out.println("Request failed with response code " + responseCode));
         }
     } catch (Exception e) {
         e.printStackTrace();  // 或者使用处理方式，如记录日志等
         System.out.println("An error occurred during request execution.");
     }
     ```

3. **数据库操作**：
   - 连接数据库，捕获可能的SQLException异常：

```java
     Connection connection = null;
     try {
         // 创建连接对象
         Class.forName("com.mysql.jdbc.Driver");
         connection = DriverManager.getConnection(
             "jdbc:mysql://localhost:3306/mydatabase",
             "username",
             "password"
         );

// 执行SQL语句
         Statement stmt = connection.createStatement();
         ResultSet rs = stmt.executeQuery("SELECT * FROM mytable");

while (rs.next()) {
             // 处理查询结果
             int id = rs.getInt("id");
             String name = rs.getString("name");

System.out.println("ID: " + id + ", Name: " + name);
         }

} catch (Exception e) {
         e.printStackTrace();
         System.out.println("An error occurred while executing SQL queries.");
     } finally {
         if (connection != null) {
             try {
                 connection.close();
             } catch (SQLException se) {
                 se.printStackTrace();
                 System.out.println("Error closing database connection.");
             }
         }
     }
     ```

以上例子展示了Java中处理不同异常情况的常见场景。在实际编程中，需要根据具体需求和异常类型进行相应的异常处理。