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ID:8976329
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时间:2018-04-13
《java练习册--类的继承》由会员上传分享,免费在线阅读,更多相关内容在应用文档-天天文库。
1、文件编号:YM/WI-19文件版本:A版文件页码:pageofjava课程实践指导书——JAVA篇JAVA语言中的类的继承一、练习目标:掌握类的继承的一般方法。二、练习时间与作业要求:本次练习一共需要180分钟。翻译练习写在JAVA笔记本上,书面作业写在JAVA家庭作业本上。后面的书面作业不包括在这个时间范围内。三、翻译练习:将下面要求翻译的内容,写在记事本上UnderstandingInheritanceAsubclassinheritsvariablesandmethodsfromitssupercla
2、ssandallofitsancestors.Thesubclasscanusethesemembersasis,oritcanhidethemembervariablesoroverridethemethods.WhatMembersDoesaSubclassInherit?Rule: Asubclassinheritsallofthemembersinitssuperclassthatareaccessibletothatsubclassunlessthesubclassexplicitlyhidesa
3、membervariableoroverridesamethod.Notethatconstructorsarenotmembersandarenotinheritedbysubclasses.Thefollowinglistitemizesthemembersthatareinheritedbyasubclass:·Subclassesinheritthosesuperclassmembersdeclaredaspublicorprotected.·Subclassesinheritthosesuperc
4、lassmembersdeclaredwithnoaccessspecifieraslongasthesubclassisinthesamepackageasthesuperclass.·Subclassesdon'tinheritasuperclass'smemberifthesubclassdeclaresamemberwiththesamename.Inthecaseofmembervariables,themembervariableinthesubclasshidestheoneinthesupe
5、rclass.Inthecaseofmethods,themethodinthesubclassoverridestheoneinthesuperclass.Creatingasubclasscanbeassimpleasincludingtheextendsclauseinyourclassdeclaration.However,youusuallyhavetomakeotherprovisionsinyourcodewhensubclassingaclass,suchasoverridingmethod
6、sorproviding文件编号:YM/WI-19文件版本:A版文件页码:pageofjava课程实践指导书implementationsforabstractmethods.HidingMemberVariablesAsmentionedintheprevioussection,membervariablesdefinedinthesubclasshidemembervariablesthathavethesamenameinthesuperclass.WhilethisfeatureoftheJaval
7、anguageispowerfulandconvenient,itcanbeafruitfulsourceoferrors.Whennamingyourmembervariables,becarefultohideonlythosemembervariablesthatyouactuallywishtohide.OneinterestingfeatureofJavamembervariablesisthataclasscanaccessahiddenmembervariablethroughitssuper
8、class.Considerthefollowingsuperclassandsubclasspair:classSuper{NumberaNumber;}classSubbieextendsSuper{FloataNumber;}TheaNumbervariableinSubbiehidesaNumberinSuper.ButyoucanaccessSuper'saNumberfromSubbiewithsup
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