Exception handling in Java (continued)

In Java programming, exception handling is a very important task. In the previous article, we have introduced the concept and classification of exceptions in Java and how to customize exception classes. This article will continue to explore exception handling in Java.

1. Grammatical structure of exception handling

In Java, the grammatical structure of exception handling is mainly divided into two types: try-catch statement and throws statement.

1. try-catch statement

The try-catch statement is used to catch and handle exceptions. The syntax structure is as follows:

try {
    //可能产生异常的代码块
} catch (ExceptionType e) {
    //处理异常的代码块
} finally {
    //可选的finally代码块
}

In the try code block, We need to write code that may throw exceptions; if an exception is caught, it will jump to the catch block that matches the exception type for processing. An exception type parameter e will be referenced in the catch block, and we can call methods for exception-related information through e. The catch block will handle one type of exception. If there are multiple exceptions that need to be handled, you can write multiple catch blocks below the try code block.

The finally block is optional and is used to execute some code that must be completed, such as releasing resources, etc. Regardless of whether an exception occurs, the code in the finally block will be executed.

2. throws statement

throws statement is used to declare methods that may throw exceptions. The syntax structure is as follows:

访问修饰符 返回类型 方法名(形参列表) throws 异常类型1, 异常类型2, ... {
    // 可能抛出异常的代码块
}

throws statement declares the method What types of exceptions may be thrown? If these exceptions are generated in the method body, they still need to be handled outside the method. If the method does not handle these exceptions correctly, the method needs to declare a throws statement to throw these exceptions to the caller of the method for processing.

2. Commonly used exception classes

Java provides many built-in exception classes, from which we can choose the appropriate exception type to handle our exceptions. The following will introduce some commonly used exception classes and their uses.

1. IllegalArgumentException

This exception will be thrown when the method parameters pass illegal data or the parameter value range is not within the allowed range defined by the method.

2. IllegalStateException

When an object is not in the appropriate state before use, such as not initialized, closed or resources have been released, etc., when a method is called, This exception will be thrown.

3. ClassNotFoundException

This exception will be thrown when trying to find the corresponding class file based on a string and the class does not exist.

4. NullPointerException

This exception will be thrown when a null object reference is used in the method.

5. IndexOutOfBoundsException

When accessing objects of types such as arrays, collection objects, or strings, this exception will be thrown when the index goes out of bounds.

In addition to the above-mentioned commonly used exception classes, there are other exception classes, such as NumberFormatException, ArithmeticException, etc. By choosing the appropriate exception class, we can better handle exceptions that may occur in our code.

3. Summary:

Exception handling is an important part of Java programming, which can make the program more robust and reliable. In the process of writing Java programs, you need to fully consider possible exceptions and rationally use exception handling syntax structures and exception classes to ensure the correctness and stability of the program.

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