Postconditions

• Condition that is true after a method has completed
• If method call is in accordance with preconditions, it must ensure that postconditions are valid
• There are two kinds of postconditions:
  1. The return value is computed correctly
  2. The object is in a certain state after the method call is completed

• /**
     Deposits money into this account.
     (Postcondition: getBalance() >= 0)
     @param amount the amount of money to deposit
     (Precondition: amount >= 0)
  */

• Don't document trivial postconditions that repeat the @return clause
• Formulate pre- and postconditions only in terms of the interface of the class

  amount <= getBalance() // this is the way to state a postcondition
  amount <= balance // wrong postcondition formulation

• Contract: If caller fulfills precondition, method must fulfill postcondition