java如何处理程序运行时的异常 java异常处理的实用编程技巧

try-catch-finally

throws

try-catch-finally

try

try

catch

catch

finally

try

catch

try {
    // 可能会抛出异常的代码
    String data = fetchDataFromNetwork();
    processData(data);
} catch (NetworkException e) {
    // 捕获网络异常
    logger.error("网络请求失败: " + e.getMessage(), e);
    // 尝试备用方案或向用户提示
    displayErrorMessage("数据加载失败，请检查网络。");
} catch (DataFormatException e) {
    // 捕获数据格式异常
    logger.error("数据格式错误: " + e.getMessage(), e);
    displayErrorMessage("数据解析异常。");
} finally {
    // 无论如何都会执行的代码，通常用于资源清理
    if (connection != null) {
        connection.close(); // 确保连接关闭
    }
}

throws

throws

InsufficientStockException

// 自定义异常示例
public class InsufficientStockException extends RuntimeException {
    private final String productId;
    private final int requestedQuantity;
    private final int availableQuantity;

    public InsufficientStockException(String productId, int requestedQuantity, int availableQuantity) {
        super("商品ID: " + productId + " 库存不足。请求数量: " + requestedQuantity + ", 可用数量: " + availableQuantity);
        this.productId = productId;
        this.requestedQuantity = requestedQuantity;
        this.availableQuantity = availableQuantity;
    }

    // 可以添加getter方法获取更多信息
}

// 使用自定义异常
public void placeOrder(String productId, int quantity) {
    int stock = getProductStock(productId);
    if (stock < quantity) {
        throw new InsufficientStockException(productId, quantity, stock);
    }
    // ... 处理订单逻辑
}

java.lang.Exception

RuntimeException

throws

try-catch

IOException

SQLException

java.lang.RuntimeException

NullPointerException

ArrayIndexOutOfBoundsException

IllegalArgumentException

throws

catch

catch

try {
    // ...
} catch (Exception e) {
    // 糟糕！什么都没做，异常被“吞”了
    // 或者 System.err.println(e.getMessage()); // 打印了，但没人管
}

catch

try {
    // ...
} catch (IOException e) {
    logger.error("文件操作失败，路径: {}", filePath, e); // 记录日志
    throw new ServiceException("无法处理文件，请稍后再试。", e); // 包装并重新抛出
}

try-catch

NumberFormatException

Integer.parseInt

StringUtils.isNumeric

// 不推荐：用异常做流程控制
try {
    int num = Integer.parseInt(input);
    // ...
} catch (NumberFormatException e) {
    // input不是数字
}

// 推荐：先校验
if (StringUtils.isNumeric(input)) {
    int num = Integer.parseInt(input);
    // ...
} else {
    // input不是数字
}

Exception

catch (Exception e)

catch

// 不推荐：过于宽泛
try { /* ... */ } catch (Exception e) { /* ... */ }

// 推荐：捕获具体类型
try { /* ... */ } catch (FileNotFoundException | IOException e) { /* ... */ }

finally

AutoCloseable

try

try

// 推荐：使用try-with-resources
try (BufferedReader reader = new BufferedReader(new FileReader("file.txt"))) {
    String line;
    while ((line = reader.readLine()) != null) {
        System.out.println(line);
    }
} catch (IOException e) {
    logger.error("读取文件失败", e);
}
// 无需手动关闭reader，它会自动关闭

RuntimeException

Exception

RuntimeException

throws

// 继承RuntimeException的自定义异常示例 (更常用)
public class UserNotFoundException extends RuntimeException {
    private final String userId;

    public UserNotFoundException(String userId) {
        super("用户ID " + userId + " 不存在。");
        this.userId = userId;
    }

    public UserNotFoundException(String userId, Throwable cause) {
        super("用户ID " + userId + " 不存在。", cause);
        this.userId = userId;
    }

    public String getUserId() {
        return userId;
    }
}

MyException

// 使用异常链和业务数据
try {
    // ... 尝试从数据库加载用户
} catch (SQLException e) {
    // 将数据库异常包装成业务异常
    throw new UserNotFoundException(userId, e); // 传入原始异常e作为cause
}

public class BusinessException extends RuntimeException {
    private final int errorCode;

    public BusinessException(int errorCode, String message) {
        super(message);
        this.errorCode = errorCode;
    }

    public int getErrorCode() {
        return errorCode;
    }
}

// 使用时
throw new BusinessException(1001, "库存不足，无法下单。");