Exception handling is the process of responding to unwanted or unexpected events when a computer program runs. Exception handling deals with these events to avoid the program or system crashing, and without this process, exceptions would disrupt the normal operation of a program.
Types of exceptions :
Exceptions can come in the following two exception classes:
1. Checked exceptions
Also called compile-time exceptions, the compiler checks these exceptions during the compilation process to confirm if the exception is being handled by the programmer. If not, then a compilation error displays on the system. Checked exceptions include SQLException and ClassNotFoundException.
2. Unchecked exceptions
Also called runtime exceptions, these exceptions occur during program execution. These exceptions are not checked at compile time, so the programmer is responsible for handling these exceptions. Unchecked exceptions do not give compilation errors. Examples of unchecked exceptions include NullPointerException and IllegalArgumentException.
Examples of exceptions
The following are examples of exceptions:
SQLException: is a checked exception that occurs while executing queries on a database for Structured Query Language syntax.
ClassNotFoundException: is a checked exception that occurs when the required class is not found -- either due to a command-line error, a missing CLASS file, or an issue with the classpath.
IllegalStateException: is an unchecked exception that occurs when an environment's state does not match the operation being executed.
IllegalArgumentException: is an unchecked exception that occurs when an incorrect argument is passed to a method.
NullPointerException: is an unchecked exception that occurs when a user tries to access an object using a reference variable that is null or empty.