This is an introductory blog to Exception Handling in Java. If you are new to exceptions or just want to refresh on some core concepts, then please continue reading!

3 TYPES OF EXCEPTIONS

1. Checked exceptions - exceptions that occur at compile time
2. Unchecked exceptions (Runtime exceptions) - occurs at time of execution
   • Include bugs, program logic, etc.
   • Are ignored at compile time
3. Errors - are not exceptions at all, but problems that occur beyond the control of the user or programmer.
   • Are typically ignored in your code

EXCEPTION HIERARCHY

• All exception classes are subtypes of the Java.Lang.Exception class
• The exception class is a subclass of the Throwable class
  • The Exception class has two main subclasses:
    • RuntimeException class
    • IOException class

CATCHING EXCEPTIONS

• Use try/catch block
• Code within try/catch block is referred to as protected code

The finally block

• The finally block follows a try or a catch block
• The finally block of code always executes
• Allows you to run any cleanup-type statements that you want to execute, no matter what happens in the protected code

USER-DEFINED EXCEPTIONS

• Rules:
  • All exceptions must be a child of Throwable
  • If you want to write a checked exception that is automatically enforced by the Handle or Declare Rule, you need to extend the Exception class.
  • If you want to write a runtime exception, you need to extend the RuntimeException class.

References

[Java - Exceptions] (https://www.tutorialspoint.com/java/java_exceptions.htm)