Language -Programming By Contract

• Contracts consist of pre- and postconditions

• Raise exceptions when violated

instance method reserveCar is public result type Boolean param fromDate type Date doc "The date the customer will collect the car."

precondition

fromDate >= System.Calendar.today and

this.isReserved = false

postcondition

result = This.isReserved

doc "Reserves this car. Returns true if" "the car could be reserved, false otherwise."

implementation

...

end implementation

end method reserveCar

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