继承性是面向对象程序设计语言不同于其他语言的最主要的特点，是子类自动共享父类数据结构和方法的机制，分为单重继承和多重继承。其中，单重继承，可用(18)来描述，多重继承的类层次结构是(19)。

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A　basic　premise　of　OGSA　is　that　everything　is(71)by　a　service:　a　network　enabled　entity　that(72)some　capability　through　the　exchange　of　messages.　Computational　resources,　storage　resources,　networks,　programs,　databases,　and　so　forth　are　all(73).　This　adoption　of　a　uniform.　service-oriented　model　means　that　all　components　of　the　environment　are　virtual.　More　specifically,　OGSA　represents　everything　as　a　Grid　service:　a　Web　service　that　conforms(74)a　set　of　conventions　and　supports　standard　interfaces　for　such　purposes　as　lifetime　management.　This　core　set　of　consistent　interfaces,　from　which　all　Grid　services　are　implemented,(75)the　construction　of　hierarchical,　higher-order　services　that　can　be　treated　in　a　uniform.　way　across　layers　of　abstraction.

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When　we　announced　Java　2　Micro　Edition(J2ME)a　few　years　ago,　we　believed　that　Java　had　an　important　role　to　play　in　hand　held　devices.　Some　were(66)that　Java　would　be　small　enough　for　such　limited　devices.　But　no(67),　Java　for　the　small　device　is　a　success.　J2ME　has　emerged　strongly　in　the　wireless　market.　Java's　portability　and　extensibility　have　brought　about　rapid(68)in　this　market.　The　success　of　Java　beyond　desktop　computers　is　significant(69)developers.　Java　literacy　is　now　more　important　than　ever,　as　Java　is　used　more　and　more　to(70)a　whole　range　of　new　computing　devices—not　only　wireless　handsets　but　also　personal　digital　assistants,　cameras,　automobiles,　home　control,　and　so　on.