JAVA练习题含答案-answer to practice 7

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1、Chapter7Inheritance13Chapter7InheritancenMultipleChoice1)Inheritanceistheprocessbywhichanewclass–knownasa_________-iscreatedfromanotherclass,calledthe_____________.(a)baseclass,derivedclass(b)derivedclass,baseclass(c)inheritedclass,baseclass(d)baseclass,inheritedclassAnswer:B2

2、)Inheritancepromotescode___________.(a)reinvention(b)reuse(c)repeats(d)alloftheaboveAnswer:B3)Thekeywordextendsindicates:(a)encapsulation(b)polymorphism(c)inheritance(d)noneoftheaboveAnswer:C4)Aderivedclassisalsocalleda(a)subclass(b)superclass(c)baseclass(d)alloftheaboveAnswer

3、:ACopyright©2004Addison-Wesley.Allrightsreserved.Chapter7Inheritance131)Asuperclassisalsocalleda(a)derivedclass(b)dominantclass(c)subclass(d)baseclassAnswer:D2)Whatdoesaderivedclassautomaticallyinheritfromthebaseclass?(a)instancevariables(b)staticvariables(c)publicmethods(d)al

4、loftheaboveAnswer:D3)Ifthefinalmodifierisaddedtothedefinitionofamethod,thismeans:(a)Themethodmayberedefinedinthederivedclass.(b)Themethodmayberedefinedinthesubclass.(c)Themethodmaynotberedefinedinthederivedclass.(d)Noneoftheabove.Answer:C4)Abaseclassissynonymouswitha:(a)Childc

5、lass(b)Parentclass(c)Derivedclass(d)SubclassAnswer:B5)Thespecialsyntaxforinvokingaconstructorofthebaseclassis:(a)super()(b)base()(c)parent()(d)child()Answer:A6)Anobjectofaderivedclasshasthetypeofthederivedclass,anditalsohasthetypeofthebaseclass,andmoregenerally,hasthetypeofeve

6、ryoneofits___________classes.(a)descendant(b)child(c)ancestor(d)subAnswer:CCopyright©2004Addison-Wesley.Allrightsreserved.Chapter7Inheritance131)Inusingthekeywordthisinplaceofsuper(),theinvocationofthismustbethe___________actiontakenbytheconstructor.(a)first(b)last(c)itdoesnot

7、matter(d)noneoftheaboveAnswer:A2)Amethodorinstancevariablemodifiedbyprotected:(a)cannotbeaccessedbynameinsideitsownclassdefinitions.(b)cannotbeaccessedbynameinsideanyclassderivedfromit.(c)cannotbeaccessedbynameinthedefinitionofanyclassinthesamepackage.(d)cannotbeaccessedbyname

8、inanyotherclass(thatis,otherthanclassesnamedina-c.).Answer:D3