Exception in Java
An exception is something that is undesirable and arises as a result of something that interferes with the normal execution of the program. Here is an example of an exception, it is an unwanted disruption during the execution of the program which leads to the termination of the program abruptly. This is unacceptable in programming languages. There are several causes of an exception. They include the instances where the user enters invalid data, a file that needs to be opened but cannot be located, or in some cases, the loss of a network connection in the middle of communication. There is more to this topic than this article can cover, for more information on the topic, you can contact our exception assignment, help team.
Difference between an error and an exception.
Both are undesirable effects that occur as a result of anomalies in the running of the program. We define an error that indicates that something severe has happened in the program. Normally, an error terminates the execution of the program while in case of an exception the program could still run. In simple words, an error is an extreme manifestation of an anomaly appearing in the code that would force the program to stop.
Categories of exceptions in Java.
There are two major types of java exceptions. These are checked exceptions and unchecked exceptions.
Checked exceptions. They are also referred to as compilation time exceptions because they normally occur during the compilation of a program. An example is if you try to read a file from the directory. If the file does not exist, then the user will be prompted before its execution.
Unchecked exceptions. They occur after the program has been executed. Thus they are referred to as runtime errors. Examples are programming bugs and logical errors.
This is one of the most important features that enable us to handle exceptions as they arise. Exceptions can be handled. In Java, we handle the error by providing meaningful information to the user about the problem at hand rather than a computer-generated message that the user might not understand. With exception handling, the execution of the program continues. It’s a guarantee that the program will continue even if the exception occurs. Perhaps, this is the main advantage of exception handling.
Built-in exceptions and custom exceptions.
Java has exceptions directly related to its libraries and allows the user to define their exceptions. The exceptions directly related to Java's built-in libraries are known as built-in exceptions, while the user-defined exceptions are known as custom exceptions. Custom expression helps the user define their own exceptions that suit their needs. Adept programmers can develop these customer exceptions to raise their own messages.
Examples of built-in exceptions are:-
ArithmeticException- occurs when some undesirable condition is found during an arithmetic operation.
RuntimeException-occurs during runtime execution.
NoSuchFieldException – occurs if the field is not found in the class.
Exception handling keywords.
There are some keywords that are normally used in error handling.
In this article, we are informing you about how they work rather than giving you a practical example of how to use them in your code.
Try keyword – This keyword specifies where we should place the exceptions code. It cannot be used on its own, and it is normally followed by other keywords such as catch and finally.
Catch keyword- This is the keyword that handles the exception. As explained above it is always preceded by the try keyword
Finally keyword - Used to execute a critical part of the program, and it executes whether the exception has been handled or not.
Throws keyword- Declares an exception in the code. It only informs the user that there may be an exception in the code.
Throw- As the name suggests, it throws an exception.
The following are some of the methods used in exceptions.
Public String to String()- Use this function when you want to get the class of the object in conjunction with the message from getMessage()
Public string getMessage () – Use this function when you want to get the full message on the exception that has occurred.
Public ThrowablegetCause() – Gives the cause of the exception.
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