详解Java中异常处理机制：try-catch-finally实例展示

原创一时失言乱红尘 2024-09-28 02:03 48阅读 0赞

在Java编程中，异常处理机制用于捕获和处理程序运行过程中出现的错误。以下是基于`try-catch-finally`结构的实例：

1. **基本使用**：
```java
public class ExceptionHandling {
    public static void main(String[] args) {
        try {
            // 可能引发异常的操作
            int divisionByZero = 10 / 0;
            System.out.println("Division by zero resulted in: " + divisionByZero);

} catch (ArithmeticException e) {
            // 处理除以零的异常
            System.out.println("Caught an ArithmeticException: " + e.getMessage());
        } finally {
            // 无论是否发生异常，这里都会执行
            System.out.println("This is executed regardless of errors.");
        }
    }
}
```
2. **使用自定义异常**：
```java
public class ExceptionHandlingWithCustomError extends Exception {
    public ExceptionHandlingWithCustomError(String message) {
        super(message);
    }
}

public class Main {
    public static void main(String[] args) {
        try {
            // 假设这里有一个可能导致自定义错误的操作
            throw new ExceptionHandlingWithCustomError("This is a custom error message.");
        } catch (ExceptionHandlingWithCustomError e) {
            System.out.println("Caught a custom exception: " + e.getMessage());
        } finally {
            System.out.println("Finally block executed regardless of errors.");
        }
    }
}
```
3. **结合finally块处理资源清理**：
```java
import java.sql.Connection;
import java.sql.DriverManager;

public class ExceptionHandlingFinalBlock {
    public static void main(String[] args) {
        Connection connection = null; // 创建连接的变量

try {
            // 驱动程序加载，获取到数据库连接
            Class.forName("com.mysql.jdbc.Driver");
            connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/testdb", "username", "password");

// 操作数据库，这里假设会引发异常
            String sql = "INSERT INTO users (name) VALUES ('New User')"; 
            connection.createStatement().execute(sql);

} catch (Exception e) {
            System.out.println("An error occurred while handling database operations: " + e.getMessage());
            
            // 如果出现数据库连接错误，需要关闭连接
            if (connection != null && !connection.isClosed()) {
                try {
                    connection.close();
                    System.out.println("Connection closed to prevent resource leak.");
                } catch (SQLException se) {
                    System.out.println("An error occurred while closing database connection: " + se.getMessage());
                }
            }
        } finally {
            // 确保无论是否发生异常，关闭数据库连接
            if (connection != null && !connection.isClosed()) {
                try {
                    connection.close();
                    System.out.println("Connection closed to prevent resource leak.");
                } catch (SQLException se) {
                    System.out.println("An error occurred while closing database connection: " + se.getMessage());
                }
            }

// 这个块确保所有资源（包括数据库连接）都已经正确地释放
        }
    }
}
```
以上实例展示了Java中`try-catch-finally`结构的基本使用，以及在处理可能引发异常的代码时如何捕获和处理这些错误。