Difference between Unchecked exception or runtime exception

Question

This was an interview question. What is the main difference between unchecked exception and error as both are not caught? They will terminate the program.

Answer 1

Checked Exception:

• The classes that extend Throwable class except RuntimeException and Error are known as checked exceptions.
• Also known as compile time exception because these type of exceptions are checked at compile time. That means if we ignore these exception (not handled with try/catch or throw the exception) then a compilation error occurred.
• They are programmatically recoverable problems which are caused by unexpected conditions outside control of code (e.g. database down, file I/O error, wrong input, etc)
• We can avoid them using try/catch block.
• Example: IOException, SQLException etc

Unchecked Exception:

• The classes that extend RuntimeException are known as unchecked exceptions
• Unchecked exceptions are not checked at compile-time rather they are checked at runtime.And thats why they are also called "Runtime Exception"
• They are also programmatically recoverable problems but unlike checked exception they are caused by faults in code flow or configuration.
• Example: ArithmeticException,NullPointerException, ArrayIndexOutOfBoundsException etc
• Since they are programming error, they can be avoided by nicely/wisely coding. For example "dividing by zero" occurs ArithmeticEceeption. We can avoid them by a simple if condition - if(divisor!=0). Similarly we can avoid NullPointerException by simply checking the references - if(object!=null) or using even better techniques

Error:

• Error refers irrecoverable situation that are not being handled by try/catch
• Example: OutOfMemoryError, VirtualMachineError, AssertionError etc.