使用try-catch-finally 可有效處理異常，確保程序穩(wěn)定運行。 1. try 塊包裹可能出錯的代碼；2. catch 塊捕獲並處理異常，應(yīng)先捕具體異常再捕通用異常；3. finally 塊無論是否發(fā)生異常都會執(zhí)行，適合資源清理。避免空捕獲、過度寬泛的catch、大範(fàn)圍try 塊及將異常用於常規(guī)流程等錯誤。此外，某些嚴(yán)重錯誤如OutOfMemoryError 無法被捕獲處理。掌握此結(jié)構(gòu)有助於提升程序健壯性。

When you're dealing with exceptions in languages like Java, C#, or JavaScript (among others), using try , catch , and finally blocks helps you manage unexpected errors gracefully. These blocks let your program attempt an operation, respond if something goes wrong, and then clean up afterward regardless of what happened.

Here's how to use them effectively.

Understanding the Role of Each Block

Each block plays a specific role:

• try : Wrap the code that might throw an exception here.
• catch : Handle the exception if one is thrown in the try block.
• finally : Always execute this block after try and catch , whether an exception occurred or not.

This structure ensures your app doesn't crash from unhandled errors and gives you control over cleanup tasks like closing files or database connections.

When and How to Use Try-Catch

Use a try-catch when you expect something might go wrong — for example, trying to read a file that may not exist, or converting user input to a number.

 try {
    int result = 10 / Integer.parseInt("zero");
} catch (NumberFormatException e) {
    System.out.println("Not a valid number.");
}

In this case:

• The string "zero" can't be converted to an integer → throws NumberFormatException .
• The catch block handles it by printing a message instead of letting the app crash.

You can also catch multiple exceptions by chaining catch blocks:

• Catch more specific exceptions first (like FileNotFoundException )
• Then more general ones (like IOException )

This prevents less specific handlers from accidentally swallowing detailed errors.

Why Finally Is Useful (Even If You Don't Always Need It)

The finally block runs no matter what — even if an exception was caught or not. That makes it perfect for resource cleanup.

For example:

 FileInputStream fis = null;
try {
    fis = new FileInputStream("data.txt");
    // do something with the file...
} catch (FileNotFoundException e) {
    System.out.println("File not found!");
} finally {
    if (fis != null) {
        try {
            fis.close();
        } catch (IOException e) {
            // handle close error
        }
    }
}

This ensures the file stream gets closed even if reading fails or throws an error.

Note: In newer versions of Java, you can simplify this using try-with-resources , but understanding finally is still important for legacy code and non-resource cases.

Common Mistakes to Avoid

There are a few pitfalls people run into when starting out:

• Catching exceptions but doing nothing — logging or at least informing the user is better than silence.
• Using overly broad catches like catch (Exception e) without good reason — this can hide bugs.
• Putting everything in one big try block — keep your try blocks small so it's clear what caused the error.
• Throwing exceptions for normal logic flow — exceptions should be exceptional, not part of regular behavior.

Also, don't forget that some exceptions can't be caught — like OutOfMemoryError . Those usually mean something serious is wrong with your environment or code.

基本上就這些。 Once you get used to wrapping risky operations in try-catch and cleaning up in finally, handling errors becomes much smoother.

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