In Java, the most common way to deal with exceptions is the try-catch-finally structure, which is the core of which is to understand the functions of each part separately and use it reasonably. 1. The try block is used to wrap code that may throw exceptions, and it should avoid containing too much irrelevant logic; 2. The catch block is captured and processed in sequence from subclass to parent class according to the specificity of the exception. It is recommended to record a log or prompt the user to avoid empty catch; 3. The finally block will be executed regardless of whether an exception occurs. It is suitable for closing resources, but be careful that it is executed before return and may not be executed in extreme cases; 4. Use multiple exception merging writing and try-with-resources to improve the simplicity and security of the code; 5. Do not swallow exceptions, at least print logs for easy debugging. Mastering these key points can effectively deal with most exception handling scenarios.
In Java, the most common way to deal with exceptions is to use try-catch-finally structure. It helps us catch and handle possible errors at runtime while ensuring resources are properly released. The key is to understand the role and usage scenarios of each part.
try block: Used to wrap the code that may have errors
try is the first step in exception handling, you put the code that may throw exceptions here. For example, reading files, network requests, or type conversion operations may have problems.
try {
int result = 10 / 0; // ArithmeticException will be thrown here
}Notice:
-
tryblock must have a correspondingcatchorfinallyblock. - Don't write too much irrelevant logic in
try, as this will easily make exceptions difficult to locate.
catch block: used to catch and handle specific exceptions
When an exception is thrown in try , Java will look for a matching catch block to handle it. You can handle it separately according to different exception types:
catch (ArithmeticException e) {
System.out.println("The divisor cannot be 0");
}
catch (Exception e) {
System.out.println("Other exception occurred:" e.getMessage());
}suggestion:
- Arrange from top to bottom according to the specific degree of the exception, first capture the subclass and then capture the parent class.
- Try not to just write a
catch (Exception e)to cover all the situations, so that the real problem can be easily concealed. - You can record logs in
catch, prompt users or make a bottom-up process, but don't do anything (empty catch).
Finally block: executes regardless of whether there is an exception or not
Regardless of whether an exception occurs or not, whether catch matches successfully, the code in finally block will always be executed. This is very suitable for closing resources such as database connections, IO streams, etc.
Finally {
if (inputStream != null) {
inputStream.close();
}
}Need to note:
- If there is a return statement in
tryorcatch, it willfinallybe executed before return. - In some extreme cases (such as a JVM crash),
finallymay not be executed.
Some tips for practical use
Multiple exception merging writing (Java 7)
If multiple exception types are handled the same way, you can write it like this:catch (IOException | SQLException e) { e.printStackTrace(); }try-with-resources (Java 7)
If you are dealing with objects that implement theAutoCloseableinterface, you can declare resources directly aftertry, and the system will automatically close, without manually writingfinally.try (FileInputStream fis = new FileInputStream("file.txt")) { // Use fis to read the file} catch (IOException e) { e.printStackTrace(); }Don't swallow the abnormalities
When writingcatch, at least print out exception information or log the log, otherwise it will be difficult to find out what the problem is during debugging.
Basically that's it. By mastering the structure and usage of try-catch-finally , you can deal with most Java exception handling scenarios. Not complicated but it is easy to ignore details, especially in resource management and exception classification.
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