Experiments

error_exception

2 min read

Exceptions and Errors

  • Exceptions and Errors both are subclasses of Throwable class.
  • Throwable:
    • Exception
    • Error
classDiagram
Throwable <|-- Exception
Throwable <|-- Error
Exception <|-- IOException
Exception <|-- RuntimeException
RuntimeException <|-- NullPointerException
Error <|-- IOError
Error <|-- VirtualMachineError
VirtualMachineError <|-- OutofMemoryError
VirtualMachineError <|-- StackOverflowError

Types

  • Errors
    • Unchecked (runtime)
  • Exceptions
    • Checked (compile time) — Code will not compile at all
    • Unchecked (runtime)

Error

  • indicates serious problems that a reasonable application should not try to catch
  • Most such errors are abnormal conditions like lack of system resources
    • It indicates serious problem in app
    • It should not be caught or handled
  • Error:
    • IOError — Serious issue with underlying filesystem
    • AssertionError —
    • VirtualMachineError — indicates JVM running out of resources
      • InternalError
      • UnknownError
      • OutOfMemoryError
      • StackOverflowError
  • It is possible to throw error but it is not recommended
try {
    throw new Error("something is wrong");
} catch (Error e) {
    System.out.println(e.getMessage()); // something is wrong
}

Exception

  • Exceptions are the problems which can occur at runtime and compile time.
  • It mainly occurs in the code written by the developers.

Checked

  • They are checked at compile time
  • All exceptions which inherit from Exception class except RuntimeException are checked
  • Exception:
    • IOException
    • ApplicationException
    • SQLException
    • CloneNotSupportedException
    • DataFormatException

Unchecked

  • They occur at runtime
  • All Exceptions which inherit RuntimeException are unchecked
  • Exception:
    • RuntimeException:
      • NullPointerException — calling an action on null object
      • ArithmeticException — invalid math operation like diving by zero
      • DateTimeException — problem while calculating a date-time.
      • UnsupportedOperationException — requested operation is not supported
      • IndexOutOfBoundsException — index is out of range.
        • ArrayIndexOutOfBoundsException
        • StringIndexOutOfBoundsException
      • IllegalArgumentException — passed an inappropriate argument.
        • NumberFormatException — failed to convert character to number

Defining Custom Exceptions

  • For Checked Exceptions you can extend Exception class
  • For Unchecked Exceptions you can extend RuntimeException class (which internally extends Exception)
public class FibonacciInputException extends Exception {
    public FibonacciInputException(String message) {
        super(message);
    }
}

Chained Exception