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ken

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– [[[JavaSpecialists 123] – Strategy Pattern with Generics:http://www.javaspecialists.co.za/archive/newsletter.do?issue=123%5D%5D –

昨日、スパークリングワインを飲みつつ Generics の使い方について悩んでいたのだけど、氷解したような気がする。getDetailedType を書くしかないので。Wadler のお墨付きがあるので安心できます。

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<div><div>Inside TaxPayer, we want to use the derived class P directly in the extortCash() method. However, the only way of getting an instance without compiler warnings is to pass it in from the subclass. We can solve this issue with a factory method called <code>getDetailedType()</code> that returns the subclass.</div></div>

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<div><div>The beauty of using generics here is that EmployeeTaxStrategy does not need to downcast anymore.</div></div>

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