Java language exception handling techniques

Java is a high-level programming language, and you will inevitably encounter various abnormal situations during programming. In order to ensure the stability and reliability of the program, Java provides an exception handling mechanism. This article will introduce various methods of exception handling in Java language.

1. The concept and classification of exceptions

Exceptions refer to some abnormal situations during program execution, such as null pointers, array out-of-bounds, file not found, etc. These situations will cause the program to Unable to execute normally. Java divides exceptions into two categories: checked exceptions and unchecked exceptions.

1. Checked exceptions

Checked exceptions refer to exceptions that can be discovered by the Java compiler during compilation. Programmers must explicitly handle exceptions in the code. This abnormality is usually caused by external factors, such as file non-existence, network interruption, etc. Checked exceptions are reflected in the code as the throws keyword and usually need to be processed using try-catch statement blocks.

2. Unchecked exceptions

Unchecked exceptions are also called runtime exceptions. They refer to exceptions that occur during the running of the program and are written by the programmer himself. caused by code. Common unchecked exceptions include null pointer exceptions, array out-of-bounds exceptions, etc. These exceptions do not need to be explicitly declared in the code. If not handled, the program will crash.

2. Common techniques for exception handling

1. try-catch statement block

try-catch statement block is one of the most common techniques for exception handling one. The try statement block contains code that may cause exceptions, and the catch statement block is used to handle exceptions. When the code in the try statement block throws an exception, the program jumps into the catch statement block for processing.

try {

// 可能抛出异常的代码

} catch (Exception e) {

// 异常处理代码

}

In Java, exceptions are divided into multiple categories. If not specified For specific exception types, the catch statement block will handle all types of exceptions. If you want to handle a certain exception specifically, you can specify the corresponding exception type, as follows:

try {

// 可能抛出IOException的代码

} catch (IOException e) {

// IOException异常处理代码

} catch (Exception e) {

// 其他异常处理代码

}

2. try-with-resources statement block

try-with-resources statement block is Java The new syntax in 7 is used to replace the traditional try-catch-finally statement block. try-with-resources can automatically close resources that implement the AutoCloseable interface, avoiding resource leakage problems caused by forgetting to close resources.

try (FileStream fs = new FileStream("data.txt")) {

// 可能抛出异常的代码

} catch (IOException e) {

// 异常处理代码

}

3. throw statement

The throw statement is used to manually throw exceptions. The exception type and its related information can be customized in the code. You can put the throw statement in the if statement to determine whether the conditions of the custom exception are met, and if so, throw the exception.

if (x < 0) {

throw new IllegalArgumentException("参数不能小于0");

}

4. throws keyword

throws keyword is used to An exception type is thrown to the superior calling method, which is handled by the superior method. Just add the throws keyword to the method declaration and specify the type of exception to be thrown.

public void readFile() throws IOException {

// 可能抛出IOException的代码

}

5. finally statement block

finally statement block is try-catch Optional statement block used to include code to clean up resources in the code. Regardless of whether the code in the try statement block is executed normally, the code in the finally statement block will be executed, which is usually used for operations such as releasing resources.

try {

// 可能出现异常的代码

} catch (Exception e) {

// 异常处理代码

} finally {

// 释放资源等清理操作

}

3. Summary

Java exception handling mechanism is an essential part of program design. It can help programmers better handle exceptions during program running, thereby improving program reliability and stability. This article introduces the classification of Java exceptions and their handling techniques, including try-catch statement blocks, throw statements, throws keywords, finally statement blocks, etc. In actual development, these methods need to be flexibly used according to specific business needs to handle exceptions in a timely manner and ensure the normal operation of the program.

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