Creating Your Own or Custom Exception Classes in java

Making the exception class

class MyException extends Exception
{
  String message;

//----------------------------------------------
// Default constructor - initializes instance variable to unknown

  public MyException()
  {
    super();             // call superclass constructor
    message = "No message,just for name";
  }
  

//-----------------------------------------------
// Constructor receives some kind of message that is saved in an instance variable.

  public MyException(String errMsg)
  {
    super(err);     // call super class constructor
    message= errMsg;  // save message
  }
  

//------------------------------------------------  
// public method, callable by exception catcher. It returns the error message.

  public String getMessage()
  {
    return message;
  }
}
  

Throwing the above exception:

Consider the following method, which takes inputString and if its not "Vaani", it throws exception.

private void checkWord(String s) throws SpellException
{
  if ("Vaani".equalsIgnoreCase(s))
    System.out.println("OK");
  else
    throw new SpellException("Word is not Vaani");
 }

Now suppose we are calling this method:

try
 {
   checkWord();   // this method throws SpellException
 }
 catch (MyException ex)   // but it is caught here
 {
   System.out.println("Spell exception was: " + ex.getMessage());
 }