Exception Hierarchies

The Throwable class is the super-class of all errors and exceptions in the Java language. Only objects that are instances of this class (or one of its sub-classes) are thrown by the Java Virtual Machine or can be thrown by the Java throw statement.

Exceptions are regular classes, and as such, one exception can sub-class another.

class BankingException extends Throwable {...}
class InsufficientFundsException extends BankingException {...}
class NegativeAmountException extends BankingException {...}

If an exception is declared to be caught, any of the sub-classes of that exception will also be caught by that same catch statement.

try {
  // Some code that might throw BankingException exception
  // or its sub-classes
} catch (BankingException e) {
  // deal with the exception
}

When you chain catch blocks, you must deal with more specific exceptions first.

try {
  // Some code that might throw BankingException exception
  // or its sub-classes
} catch (InsufficientFundsException e) {
  // deal with InsufficientFundsException
} catch (BankingException e) {
  // deal with the exception
}