Exception handling and error handling needs to be done for a fully-working application.
Try-Catch-Finally
The general syntax is as follows:
try {
}
catch (Exception e) {
}
finally {
}The try block attempts to run a few lines of code. If an exception is thrown by any of the lines, the catch block is invoked. Multiple catch blocks can be written to handle different kinds of exceptions. The finally block is for housekeeping.
Unchecked and Checked Exceptions
An unchecked exception is an exception caused by a programmer’s errors, while a checked exception is an exception that a programmer has no control over.
All unchecked exceptions in Java are subclasses of RuntimeException, while checked exceptions are subclasses of Exception.
Throwing Exceptions
To indicate that a method could throw exceptions, the keyword throws should be in its method declaration, like such:
public calculateBMI(double height, double weight) throws IllegalArgumentException
Catching Exceptions
If a method that generates an exception is called, the exception does not need to be handled within the function it is called in, as it can be handled by the method that calls in.
An unchecked exception, if not caught, will propagate automatically down the stack until it is caught, or if it is not caught, will result in an error message.
Overriding
With regards to overriding, the overriding method must throw only the same, or a more specific exception than the overriding method to ensure that the LSP is followed.
Good Practices
Catch Exceptions to Clean Up
It is better to catch the exceptions in some cases rather than to pass the exceptions down to other methods.
Do Not Catch Them All
Do not just catch the Exception superclass, as it silently ignores all kinds of exceptions, which will make it more difficult to determine errors in the program.
Do Not Overreact
Do not exit a program because of an exception. Instead, do the required housekeeping needed.
Do Not Break Abstraction Barrier
Letting the calling method handle the exception causes the implementation details to be leaked, making it harder to change implementation in future.
Implementation-specific exceptions should be handled within the abstraction barrier.
Do Not Use Exception Handling as a Control-Flow Mechanism
Do not use exceptions as a form of if-conditions.