Designing Your Own Exception Types

• You can design your own exception types–subclasses of Exception or RuntimeException

• if (amount > balance)
  {
     throw new InsufficientFundsException(
        "withdrawal of " + amount + " exceeds balance of " + balance);
  }

• Make it an unchecked exception–programmer could have avoided it by calling getBalance first
• Extend RuntimeException or one of its subclasses
• Supply two constructors
  1. Default constructor
  2. A constructor that accepts a message string describing reason for exception