The key to handling Java exceptions is reasonable response rather than simple capture. First, do not ignore exceptions silently, at least print logs or retow; second, distinguish between recoverable and unrecoverable exceptions. The former uses checked exceptions, and the latter uses unchecked exceptions; third, avoid excessive use of try-catch, and problems that can be prevented should be checked in advance; finally, properly encapsulate custom exceptions to improve maintainability and context clarity.
When dealing with Java exceptions, many people know how to try-catch, but not many people really use the exception mechanism well. The key is not to catch the exception, but how to respond reasonably.
Don't swallow the abnormalities easily
Sometimes in order to prevent the program from crashing, we will write an empty catch block, such as:
try {
// Possible error code} catch (Exception e) {}This seems safe, but in fact it makes the problem "disappear". You won't know what's wrong, and you can't start debugging. At least the log should be printed, or more explicit information should be thrown.
suggestion:
- Never ignore exceptions silently.
- Use
e.printStackTrace()or log framework to record information (such as log4j, slf4j). - If it does not really require processing, it can be re-throwed or wrapped into a runtime exception.
Distinguish between recoverable and unrecoverable exceptions
Java has checked exception and unchecked exception. Simply put, the former is something you have to deal with (such as IOException), and the latter is a problem that is exposed only at runtime (such as NullPointerException).
Many people abuse checked exception, resulting in bloated code. In fact, it should be judged based on the scene:
- Recoverable exceptions (such as network timeout): Use checked exception, the caller needs to handle it explicitly.
- Unrecoverable exceptions (such as parameter errors): It is more appropriate to use unchecked exception to avoid forced processing.
Example: If you write a tool method that receives string parameters but passes in null, it is reasonable to throw IllegalArgumentException .
Don't overuse try-catch
Sometimes you will see code like this:
try {
int result = a / b;
} catch (ArithmeticException e) {
// Handle zero-deletion error}In fact, in this case, it is possible to check whether b is 0 in advance, rather than relying on the exception mechanism. Exception handling is not a replacement for process control.
Common misunderstandings:
- Use exceptions to control logical flow (such as reading a file to throw exceptions to the end)
- Frequent try-catch in loops affects performance
suggestion:
- Prevent problems that can be prevented as much as possible.
- It is truly used for "unexpected situations", such as IO errors, database connection failures, etc.
Properly encapsulate and customize exceptions
After the project becomes large, throwing the underlying exception (such as SQLException) will be difficult for the caller to understand. At this time, you can consider encapsulating a layer of your own exception class.
For example, you can define:
public class DataAccessException extends RuntimeException {
public DataAccessException(String message, Throwable cause) {
super(message, cause);
}
}Then, the exception type is uniformly converted in the DAO layer.
benefit:
- Isolate the underlying implementation details
- Unify the exception system to facilitate upper-level processing
- Business-related context information can be added
Basically that's it. Exception handling seems simple, but it is not easy to do it correctly and finely.
The above is the detailed content of Effective Java Exception Handling Techniques. For more information, please follow other related articles on the PHP Chinese website!
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