DEV475 Mastering Object-Oriented Analysis and Design with UML ...

Module 2 - Concepts of Object OrientationExample: PolymorphismExample: PolymorphismfinancialInstrument.getCurrentValue()getCurrentValue()getCurrentValue()getCurrentValue()Stock Bond Mutual FundMastering Object Oriented Analysis and Design with UMLCopyright © 2003 Rational Software, all rights reserved 29In this example, a requesting object would like to know the current value of afinancial instrument. However, the current value for each financial instrument iscalculated in a different fashion. The stock needs to determine the current askingprice in the financial market that it is listed under. The bond needs to determine thetime to maturity and interest rates. A mutual fund needs to look up the closing pricefor the day from the fund management company.In a non object-oriented development environment, we would write code that maylook something like this:IF financialInstrument = Stock THENcalcStockValue()IF financialInstrument = Bond THENcalcBondValue()IF financialInstrument = MutualFund THENcalcMutualFundValue()With object technology, each financial instrument can be represented by a class, andeach class will know how to calculate its own value. The requesting object simplyneeds to ask the specific object (for example, Stock) to get its current value. Therequesting object does not need to keep track of three different operation signatures.It only needs to know one. Polymorphism allows the same message to be handled indifferent ways, depending on the object that receives it.2 - 29