Java exception handling: try-catch, finally and throws

Java exception handling is a very important part of Java programming. Exceptions refer to unexpected errors or exceptions during the execution of the program. In Java, each exception has a corresponding exception class. When an exception occurs in the business logic, the corresponding exception class will be thrown.

The exception handling mechanism in Java mainly includes three methods: try-catch, finally and throws. This article will introduce in detail the use of these three methods and the precautions.

1. try-catch

try-catch is the most commonly used method in Java exception handling. Its basic syntax is as follows:

try {
    // 可能会抛出异常的代码块
} catch (Exception e) {
    // 处理异常的代码块
} finally {
    // 不管是否出现异常，都会执行的代码块
}

Among them, The try block contains code that may throw an exception. If the code is executed normally, no exception will be generated, but if an exception occurs, it will be caught by the catch block.

The catch block is used to handle exceptions that may occur. The code in the catch block can handle exceptions and record logs.

The code contained in the finally block will be executed regardless of whether an exception occurs. It is generally used for operations such as closing files and releasing resources. The finally block is often called a post-exception cleanup block, indicating that some additional cleanup work needs to be done after the exception handling is completed.

When using the try-catch statement, you need to pay attention to the following points:

• In the try code block, except for the code that may throw an exception, there must be no other exceptions. Code that may throw exceptions, otherwise there will be confusion in exception handling;
• If there are multiple catch code blocks, be sure to put the special exceptions in front, otherwise they may be blocked by more common exceptions. captured.
• The finally code block must be after the try block and catch block and cannot be used alone.

2. finally

Compared to the try-catch mechanism, the finally statement block will be executed regardless of exceptions involved. The finally statement block is mainly used for resources. freed. As long as the resource must be used while the program is running, it will be necessary to release the resource in the finally code block.

finally syntax format is as follows:

try {
    // 可能会抛出异常的代码块
} catch (Exception e) {
    // 处理异常的代码块
} finally {
    // 释放资源
}

3. throws

In Java programs, sometimes a method can be used when it is not sure how to handle an exception. throws declares the exceptions that may be thrown by this method. In this way, when calling this method, you need to use a try-catch statement to handle possible exceptions.

The throws syntax format is as follows:

[public] [static] 返回值类型 方法名(参数列表)[throws 异常列表] {
    // 代码块
}

The exception list consists of multiple exception types separated by commas, indicating a list of exception types that may be thrown by this method.

It should be noted that throws only declares which exceptions this method will throw, but it does not handle exceptions like try-catch. If the method throws an exception, it needs to be handled by its caller.

Summary:

In Java programming, exception handling is very important, which can effectively protect the program and avoid direct crash when problems occur. try-catch, finally and throws are the three main methods of Java exception handling. Each method has its applicable scenarios and precautions. When using it, you need to make a selection based on the needs of the business logic to better ensure the stability of the program.

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