FileNotFoundException in Java Exception Handling And Resolution Example
FileNotFoundException In Java: In this article, we’re going to talk about a very common exception in Java – the FileNotFoundException. we can get this exception when we try to access the file but the file is not present in that location,
Possible Reasons For FileNotFound Exception
There are a few possible reasons for getting this type of exception, here are some:
- A File may be present or not in the mentioned path
- A file with the specified pathname does exist but is inaccessible for some reason (requested writing for a read-only file, or permissions don’t allow accessing the file)
FileNotFoundException in Java
This exception will be thrown by the FileInputStream, FileOutputStream, and RandomAccessFile constructors when a file with the specified pathname does not exist. It will also be thrown by these constructors if the file does exist but for some reason is inaccessible, for example when an attempt is made to open a read-only file for writing.
Check Also: Scientific Games Interview Questions
we will get this exception when we are trying to access a file that does not exist. for access to the files, we are using classes like FileInputStream, FileOutputStream, and RandomAccessFile. The main function of these classes is used to obtain the bytes from a file system.
package co.java.exception; import java.io.File; import java.io.FileReader; public class FileNotFoundException < @SuppressWarnings("unused") public static void main(String[] args) throws java.io.FileNotFoundException < File file = new File("E://file.txt"); @SuppressWarnings("resource") FileReader fr = new FileReader(file); >> Let’s Run the above program
After execution we get an error:
Exception in thread "main" java.io.FileNotFoundException: E:\file.txt (The system cannot find the file specified) at java.io.FileInputStream.open0(Native Method) at java.io.FileInputStream.open(Unknown Source) at java.io.FileInputStream.<init>(Unknown Source) at java.io.FileReader.<init>(Unknown Source) at co.java.exception.FileNotFoundException.main(FileNotFoundException.java:12)
How to Deal FileNotFound Exception
- Once you got this exception than the first thing you need to check the path which you mentioned in your program to verify that the specified file is present or not in the mentioned path.
- if the file is present in the specified location but still you got the error then you need to check error message for confirming is there any mention about permission related issues if there are some permission related issues then you need to fix that issue or you need to verify that file is used by other application or not.
- Alert a user with a dialogue or error message: this isn’t a stop execution error, so just notifying is enough
- Just log an error: this error should not stop the execution but you log it for future analysis
in this post, we’ve seen when a FileNotFoundException can occur and several options to handle it. if still, you have any doubts then feel free to drop your question in the comment section.
FileNotFoundException in Java
The Kubernetes ecosystem is huge and quite complex, so it’s easy to forget about costs when trying out all of the exciting tools.
To avoid overspending on your Kubernetes cluster, definitely have a look at the free K8s cost monitoring tool from the automation platform CAST AI. You can view your costs in real time, allocate them, calculate burn rates for projects, spot anomalies or spikes, and get insightful reports you can share with your team.
Connect your cluster and start monitoring your K8s costs right away:
We rely on other people’s code in our own work. Every day.
It might be the language you’re writing in, the framework you’re building on, or some esoteric piece of software that does one thing so well you never found the need to implement it yourself.
The problem is, of course, when things fall apart in production — debugging the implementation of a 3rd party library you have no intimate knowledge of is, to say the least, tricky.
Lightrun is a new kind of debugger.
It’s one geared specifically towards real-life production environments. Using Lightrun, you can drill down into running applications, including 3rd party dependencies, with real-time logs, snapshots, and metrics.
Learn more in this quick, 5-minute Lightrun tutorial:
Slow MySQL query performance is all too common. Of course it is. A good way to go is, naturally, a dedicated profiler that actually understands the ins and outs of MySQL.
The Jet Profiler was built for MySQL only, so it can do things like real-time query performance, focus on most used tables or most frequent queries, quickly identify performance issues and basically help you optimize your queries.
Critically, it has very minimal impact on your server’s performance, with most of the profiling work done separately — so it needs no server changes, agents or separate services.
Basically, you install the desktop application, connect to your MySQL server, hit the record button, and you’ll have results within minutes:
DbSchema is a super-flexible database designer, which can take you from designing the DB with your team all the way to safely deploying the schema.
The way it does all of that is by using a design model, a database-independent image of the schema, which can be shared in a team using GIT and compared or deployed on to any database.
And, of course, it can be heavily visual, allowing you to interact with the database using diagrams, visually compose queries, explore the data, generate random data, import data or build HTML5 database reports.
The Kubernetes ecosystem is huge and quite complex, so it’s easy to forget about costs when trying out all of the exciting tools.
To avoid overspending on your Kubernetes cluster, definitely have a look at the free K8s cost monitoring tool from the automation platform CAST AI. You can view your costs in real time, allocate them, calculate burn rates for projects, spot anomalies or spikes, and get insightful reports you can share with your team.
Connect your cluster and start monitoring your K8s costs right away:
We’re looking for a new Java technical editor to help review new articles for the site.
1. Introduction
In this article, we’re going to talk about a very common exception in Java – the FileNotFoundException.
We’ll cover the cases when it can occur, possible ways of treating it and some examples.
2. When Is the Exception Thrown?
As indicated on Java’s API documentation, this exception can be thrown when:
- A file with the specified pathname doesnot exist
- A file with the specified pathname does exist butis inaccessible for some reason (requested writing for a read-only file, or permissions don’t allow accessing the file)
3. How to Handle It?
First of all, taking into account that it extends java.io.IOException that extends java.lang.Exception, you will need to deal with it with a try-catch block as with any other checked Exception.
Then, what to do (business/logic related) inside the try-catch block actually depends on what you need to do.
- Rise a business-specific exception: this may be a stop execution error, but you will leave the decision in the upper layers of the application (don’t forget to include the original exception)
- Alert a user with a dialogue or error message: this isn’t a stop execution error, so just notifying is enough
- Create a file: reading an optional configuration file, not finding it and creating a new one with default values
- Create a file in another path: you need to write something and if the first path is not available, you try with a fail-safe one
- Just log an error: this error should not stop the execution but you log it for future analysis
4. Examples
Now we’ll see some examples, all of which will be based on the following test class:
public class FileNotFoundExceptionTest < private static final Logger LOG = Logger.getLogger(FileNotFoundExceptionTest.class); private String fileName = Double.toString(Math.random()); protected void readFailingFile() throws IOException < BufferedReader rd = new BufferedReader(new FileReader(new File(fileName))); rd.readLine(); // no need to close file >class BusinessException extends RuntimeException < public BusinessException(String string, FileNotFoundException ex) < super(string, ex); >> >4.1. Logging the Exception
If you run the following code, it will “log” the error in the console:
@Test public void logError() throws IOException < try < readFailingFile(); >catch (FileNotFoundException ex) < LOG.error("Optional file " + fileName + " was not found.", ex); >>4.2. Raising a Business Specific Exception
Next, an example of raising a business-specific exception so that the error can be handled in the upper layers:
@Test(expected = BusinessException.class) public void raiseBusinessSpecificException() throws IOException < try < readFailingFile(); >catch (FileNotFoundException ex) < throw new BusinessException( "BusinessException: necessary file was not present.", ex); >>4.3. Creating a File
Finally, we’ll try to create the file so it can be read (maybe for a thread that is continuously reading a file), but again catching the exception and handling the possible second error:
@Test public void createFile() throws IOException < try < readFailingFile(); >catch (FileNotFoundException ex) < try < new File(fileName).createNewFile(); readFailingFile(); >catch (IOException ioe) < throw new RuntimeException( "BusinessException: even creation is not possible.", ioe); >> >5. Conclusion
In this quick writeup, we’ve seen when a FileNotFoundException can occur and several options to handle it.
As always, the full examples are over on Github.
Slow MySQL query performance is all too common. Of course it is. A good way to go is, naturally, a dedicated profiler that actually understands the ins and outs of MySQL.
The Jet Profiler was built for MySQL only, so it can do things like real-time query performance, focus on most used tables or most frequent queries, quickly identify performance issues and basically help you optimize your queries.
Critically, it has very minimal impact on your server’s performance, with most of the profiling work done separately — so it needs no server changes, agents or separate services.
Basically, you install the desktop application, connect to your MySQL server, hit the record button, and you’ll have results within minutes:
Исключение FileNotFoundException в Java
Краткое и практическое руководство по FileNotFoundException в Java.
1. введение
В этой статье мы поговорим об очень распространенном исключении в Java – исключении FileNotFoundException .
Мы рассмотрим случаи, когда это может произойти, возможные способы лечения и некоторые примеры.
2. Когда Возникает исключение?
Как указано в документации API Java, это исключение может быть вызвано, когда:
- Файл с указанным именем пути не существуетне существует
- Файл с указанным именем пути существует , но недоступен по какой-либо причине (запрошена запись для файла только для чтения или разрешения не позволяют получить доступ к файлу)
3. Как с Этим справиться?
Прежде всего, принимая во внимание, что он расширяет java.io.IOException , который расширяет java.lang.Исключение , вам нужно будет справиться с ним с помощью блока try-catch , как и с любым другим проверенным E xception .
Затем, что делать (связано с бизнесом/логикой) внутри блока try-catch на самом деле зависит от того, что вам нужно сделать.
Возможно, вам это понадобится:
- Создание исключения для конкретного бизнеса: это может быть ошибка stopexecutionerror, но вы оставите решение в верхних слоях приложения (не забудьте включить исходное исключение)
- Предупредите пользователя диалогом или сообщением об ошибке: это не ошибка stopexecutionerror, поэтому достаточно просто уведомить
- Создание файла: чтение необязательного файла конфигурации, его поиск и создание нового файла со значениями по умолчанию
- Создайте файл по другому пути: вам нужно что-то написать, и если первый путь недоступен, попробуйте использовать отказоустойчивый
- Просто зарегистрируйте ошибку: эта ошибка не должна останавливать выполнение, но вы регистрируете ее для дальнейшего анализа
4. Примеры
Теперь мы рассмотрим несколько примеров, все из которых будут основаны на следующем тестовом классе:
public class FileNotFoundExceptionTest < private static final Logger LOG = Logger.getLogger(FileNotFoundExceptionTest.class); private String fileName = Double.toString(Math.random()); protected void readFailingFile() throws IOException < BufferedReader rd = new BufferedReader(new FileReader(new File(fileName))); rd.readLine(); // no need to close file >class BusinessException extends RuntimeException < public BusinessException(String string, FileNotFoundException ex) < super(string, ex); >> >
4.1. Регистрация исключения
Если вы запустите следующий код, он “зарегистрирует” ошибку в консоли:
@Test public void logError() throws IOException < try < readFailingFile(); >catch (FileNotFoundException ex) < LOG.error("Optional file " + fileName + " was not found.", ex); >> 4.2. Создание исключения для конкретного бизнеса
Далее приведен пример создания исключения для конкретного бизнеса, чтобы ошибка могла быть обработана на верхних уровнях:
@Test(expected = BusinessException.class) public void raiseBusinessSpecificException() throws IOException < try < readFailingFile(); >catch (FileNotFoundException ex) < throw new BusinessException( "BusinessException: necessary file was not present.", ex); >>
4.3. Создание файла
Наконец, мы попытаемся создать файл, чтобы его можно было прочитать (возможно, для потока, который непрерывно читает файл), но снова поймаем исключение и обработаем возможную вторую ошибку:
@Test public void createFile() throws IOException < try < readFailingFile(); >catch (FileNotFoundException ex) < try < new File(fileName).createNewFile(); readFailingFile(); >catch (IOException ioe) < throw new RuntimeException( "BusinessException: even creation is not possible.", ioe); >> >
5. Заключение
В этой быстрой записи мы видели, когда может возникнуть исключение FileNotFoundException и несколько вариантов его обработки.
Как всегда, полные примеры находятся на Github .