java练习册--类的继承

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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