摘要：
Holding Your Objects ___ In general, your programs will always be creating new objects based on some criteria that will be known only at run time. You 阅读全文
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Inner Classes ___ It allows you to group classes that logically belong together and to control the visibility of one within the other. It knows about 阅读全文
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Polymorphism ___ Abstract classes and methods If you have an abstract class, objects of that specific class almost always have no meaning. You create 阅读全文
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Polymorphism ___ The polymorphic method call allows one type to express its distinction from another, similar type, as long as they’re both derived fr 阅读全文
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Reusing Classes ___ The first is composition，You’re simply reusing the functionality of the code, not its form. The second approach is inheritance，You 阅读全文
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Access Control ___ A piece of work isn’t good until it’s been rewritten, often many times. Thus a primary consideration in object oriented design is t 阅读全文
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Initialization & Cleanup ___ Guaranteed initialization with the constructor In Java, the class designer can guarantee initialization of every object b 阅读全文