Name: Java 教程 - 修復 StackOverflow 錯誤 (Java Tutorial - Fixing StackOverflow Errors)
Uploaded: 2025-08-08T18:34:04.000Z
Duration: 6 min 10 s

We are going to look at code that could trigger an error.

我們將查看可能引發錯誤的代碼。

Recall that an error is a subset of throwables.

回顧一下，錯誤是可拋物的一個子集。

They aren't an object that can be thrown by an app indicating a serious problem.

它們不是應用程序在出現嚴重問題時拋出的對象。

You will look specifically at a stack overflow error and the best way to handle it.

您將具體瞭解堆棧溢出錯誤以及處理該錯誤的最佳方法。

Errors are throwables that should not be handled by an app and indicate an unrecoverable issue with your application.

錯誤是應用程序不應處理的拋出物，表示應用程序出現了無法恢復的問題。

Stack overflow error is an example of a virtual machine error, indicating that the Java virtual machine or JVM has run out of some kind of resource.

堆棧溢出錯誤是虛擬機錯誤的一個例子，表示 Java 虛擬機或 JVM 的某種資源用完了。

In this case, the stack for the app has overflowed.

在這種情況下，應用程序的堆棧已經溢出。

To see this error in action, I created an app that involves the Fibonacci sequence.

為了瞭解這種錯誤的實際效果，我創建了一個涉及斐波那契數列的應用程序。

The Fibonacci sequence is a mathematical series of numbers where each number in the series is the sum of the two preceding numbers. 1 plus 1 equals 2, 1 plus 2 equals 3, 2 plus 3 equals 5, and so on.

斐波那契數列是一個數學數列，數列中的每個數字都是前兩個數字之和。1 加 1 等於 2，1 加 2 等於 3，2 加 3 等於 5，以此類推。

Now that we know what Fibonacci sequence is, let's review an existing Spring Boot app that provides an endpoint for a REST API that takes the number n and returns the nth number of the Fibonacci sequence.

既然我們已經知道了什麼是斐波那契數列，讓我們回顧一下現有的 Spring Boot 應用程序，它為 REST API 提供了一個端點，該端點接收數字 n 並返回斐波那契數列的第 n 個數字。

If we pass in 6 as n to our endpoint in our app, it will return 8, because 8 is the sixth number in the Fibonacci sequence.

如果我們在應用程序中將 6 作為 n 發送給端點，它將返回 8，因為 8 是斐波納契數列中的第六個數字。

Generating a Fibonacci sequence is a great way to learn and understand recursion.

生成斐波那契數列是學習和了解遞歸的好方法。

And recursing incorrectly could lead to a stack overflow error.

錯誤遞歸可能導致堆棧溢出錯誤。

I highly recommend reviewing recursion through a few of our other videos and courses we have available.

我強烈建議大家通過我們的其他視頻和課程來複習遞歸。

In our code for this app, I have a standard Java Spring app showing in my IDE with a controller using the REST controller annotation seen on line 6.

在這個應用程序的代碼中，我的集成開發環境中顯示了一個標準的 Java Spring 應用程序，其中的控制器使用了第 6 行中的 REST 控制器註解。

This controller provides an endpoint defined on line 16 that takes in a request parameter of n.

該控制器提供了一個定義在第 16 行的端點，該端點接收的請求參數為 n。

This method returns a response entity with the HTTP status of OK on line 18, with the body of the response containing the nth number of the Fibonacci sequence.

該方法在第 18 行返回 HTTP 狀態為 OK 的響應實體，響應正文包含斐波那契數列的第 n 個數字。

This findFibonacciNumber method uses a private helper method called Fibonacci, which is defined on line 27, and it returns the nth number of the sequence.

這個 findFibonacciNumber 方法使用了第 27 行定義的名為 Fibonacci 的私有輔助方法，它返回序列的第 n 個數字。

The Fibonacci method is where we introduce recursion, where the method calls itself repeatedly to do a piece of work, which we see on line 29.

在斐波納契方法中，我們引入了遞歸，即方法重複調用自身來完成一項工作，我們在第 29 行看到了這一點。

If we were to have a position endpoint to this method set to 3, we would call the Fibonacci method again to find the Fibonacci number in the second position, which we can see in the equation on the left side of line 28.

如果我們將此方法的位置端點設置為 3，我們就會再次調用斐波那契方法來查找第二個位置上的斐波那契數字，我們可以在第 28 行左邊的等式中看到這一點。

And we would call the Fibonacci method again to get the first number in this sequence, which is the right side of this equation on line 29.

我們將再次調用斐波那契方法，得到序列中的第一個數字，也就是第 29 行等式的右邊。

Do you notice a potential mistake in how this method is implemented?

您是否注意到這種方法在實施過程中可能存在錯誤？

Let's run the application and try the endpoint to see what happens.

讓我們運行應用程序並嘗試端點，看看會發生什麼。

I know that my application is running because I see started Fibonacci application at the bottom of my console here in my IDE.

我知道我的程序正在運行，因為我在 IDE 的控制檯底部看到了已啟動的 Fibonacci 程序。

I'm running my app through my IDE, but you can also run it via command line, or however you prefer to run your app.

我通過集成開發環境運行應用程序，但你也可以通過命令行或其他你喜歡的方式運行應用程序。

I like using Postman, which is a GUI or a graphical user interface for submitting various kinds of requests to APIs.

我喜歡使用 Postman，它是一個 GUI 或圖形用戶界面，用於嚮應用程序接口提交各種請求。

You can, of course, use whatever method you prefer.

當然，您可以使用自己喜歡的任何方法。

With this, I can use the URL localhost8080 slash Fibonacci slash find a number question mark n equals three to get the third number of the sequence, which should be two.

有了它，我就可以使用網址 localhost8080 斜線斐波那契斜線查找數字問號 n 等於 3 來得到序列的第三個數字，應該是 2。

We get a 500 internal Silver error as seen in the bottom of our Postman response.

從 Postman 響應的底部可以看到，我們收到了 500 內部 Silver 錯誤。

Back in the console log of our app, note that the stack trace has many, many lines pointing to line 29 in our controller.

回到我們應用程序的控制檯日誌，注意堆棧跟蹤中有很多行都指向控制器中的第 29 行。

This is because we are using recursion and never stop recursing, leading us to continue to use more and more of the stack.

這是因為我們正在使用遞歸，而且遞歸永不停止，導致我們不斷使用越來越多的堆棧。

And so the JVM no longer has space to use.

At the top here, we see the dreaded stack overflow error.

在頂部，我們看到了可怕的堆棧溢出錯誤。

Errors are not likely at all recoverable.

So the best way to handle them is to fix them or prevent them.

是以，處理這些問題的最好辦法就是解決或預防它們。

In our case, this means adding an if statement in our Fibonacci helper method.

在我們的例子中，這意味著在斐波納契輔助方法中添加一個 if 語句。

If our position is equal to or less than one, we just want to return the position variable itself.

如果我們的位置等於或小於 1，我們只想返回位置變量本身。

Now, let's restart our application and see if our code change was successful.

現在，讓我們重啟應用程序，看看代碼修改是否成功。

Now that our application is started, again, because I see started Fibonacci application at the bottom of my console, I will try the request again.

現在我們的應用程序已經啟動，因為我在控制檯底部看到了已啟動的 Fibonacci 應用程序，所以我將再次嘗試請求。

In success, we get back the result of two, which we expect, and there are no more stack overflow errors.

成功後，我們得到的結果是 2，這是我們所期望的，而且不再出現堆棧溢出錯誤。

For other errors, we will have to figure out the cause, much like we did here, and make corrections within our app.

對於其他錯誤，我們必須找出原因，就像我們在這裡所做的那樣，並在應用程序中進行修正。

You now understand what could lead to a stack overflow error and understand the best way to handle all types of errors.

現在，您已經瞭解了導致堆棧溢出錯誤的原因，並掌握了處理各類錯誤的最佳方法。