Handling exceptions

In Java, when things go wrong, they can be classified as errors or exceptions. An error is a problem that cannot be recovered from. An exception is an error that can be detected in your code such that you can possibly recover from it. For example, a recursion that never ends will result in a StackOverflowError-type error. Converting the Bob string to an integer will result in a NumberFormatException exception.

Here is a diagram of the primary exception classes:

Figure 7.1 – The exception hierarchy

Exceptions are objects of classes named after the type of exception that has occurred. In the diagram, you can see that at the root of the hierarchy is the Throwable class. From Throwable, we have two subclasses: Error and Exception. The subclasses of Error are named after the errors that may occur during program execution. These are errors that generally cannot be recovered from and should lead to the program ending.

As it may...