采用闭式洒水喷头的自动喷水灭火系统，它可分为（）。

1.importjava.util.*；2.publicclassTestSet{3.enumExample{ONE，TWO，THREE}4.publicstaticvoidmain（String[]args）{5.Collectioncoll=newArrayList（）；6.coll.add（Example.THREE）；7.coll.add（Example.THREE）；8.coll.add（Example.THREE）；9.coll.add（Example.TWO）；10.coll.add（Example.TWO）；11.coll.add（Example.ONE）；12.Setset=newHashSet（coll）；13.}14.}Whichstatementistrueaboutthesetvariableonline12？（）

A.Thesetvariablecontainsallsixelementsfromthecollcollection，andtheorderisguaranteedtobepreserved.

B.Thesetvariablecontainsonlythreeelementsfromthecollcollection，andtheorderisguaranteedtobepreserved.

C.Thesetvariablecontainsallsixelementsfromthecoilcollection，buttheorderisNOTguaranteedtobepreserved.

D.Thesetvariablecontainsonlythreeelementsfromthecoilcollection，buttheorderisNOTguaranteedtobepreserved.

importjava.util.*；publicclassWrappedString{privateStrings；publicWrappedString（Strings）{this.s=s；}publicstaticvoidmain（String[]args）{HashSeths=newHashSet（）；WrappedStringws1=newWrappedString（”aardvark”）；WrappedStringws2=newWrappedString（”aardvark”）；Strings1=newString（”aardvark”）；Strings2=newString（”aardvark”）；hs.add（ws1）；hs.add（ws2）；hs.add（s1）；hs.add（s2）；System.out.println（hs.size（））；}}Whatistheresult？（）

A.0

B.1

C.2

D.3

E.4

F.Compilationfails.

G.Anexceptionisthrownatruntime.

importjava.util.*；publicclassPQ{publicstaticvoidmain（String[]args）{PriorityQueuepq=newPriorityQueue（）；pq.add（”carrot”）；pq.add（”apple”）；pq.add（”banana”）；System.out.println（pq.poll（）+”：”+pq.peek（））；}}Whatistheresult？（）

A.apple：apple

B.carrot：apple

C.apple：banana

D.banana：apple

E.carrot：carrot

F.carrot：banana

1.importjava.util.*；2.publicclassExample{3.publicstaticvoidmain（String[]args）{4.//insertcodehere5.set.add（newinteger（2））；6.set.add（newinteger（l））；7.System.out.println（set）；8.}9.}Whichcode，insertedatline4，guaranteesthatthisprogramwilloutput[1，2]？（）

A.Setset=newTreeSet（）；

B.Setset=newHashSet（）；

C.Setset=newSortedSet（）；

D.Listset=newSortedList（）；

E.Setset=newLinkedHashSet（）；

10.interfaceJumper{publicvoidjump（）；}......20.classAnimal{}......30.classDogextendsAnimal{31.Tailtail；32.}......40.classBeagleextendsDogimplementsJumper{41.publicvoidjump（）{}42.}.......50.classCatimplementsJumper{51.publicvoidjump（）{}52.}Whichthreearetrue？（）

A.Catis-aAnimal

B.Catis-aJumper

C.Dogis-aAnimal

D.Dogis-aJumper

E.Cathas-aAnimal

F.Beaglehas-aTail

G.Beaglehas-aJumper

A.Inheritancerepresentsanis-arelationship.

B.Inheritancerepresentsahas-arelationship.

C.Interfacesmustbeusedwhencreatingahas-arelationship.

D.Instancevariablescanbeusedwhencreatingahas-arelationship.

A.Has-arelationshipsshouldneverbeencapsulated.

B.Has-arelationshipsshouldbeimplementedusinginheritance.

C.Has-arelationshipscanbeimplementedusinginstancevariables.

D.Is-arelationshipscanbeimplementedusingtheextendskeyword.

E.Is-arelationshipscanbeimplementedusingtheimplementskeyword.

F.Anarrayoracollectioncanbeusedtoimplementaone-to-manyhas-arelationship.

G.TherelationshipbetweenMovieandActressisanexampleofanis-arelationship.

A.Thiscodewillcompile.

B.Thiscodedemonstratesproperdesignofanis-arelationship.

C.Thiscodedemonstratesproperdesignofahas-arelationship.

D.AJavaprogrammerusingtheTeamclasscouldremovePlayerobjectsfromaTeamobject.

10.publicclassSuperCaic{11.protectedstaticintmultiply（inta，intb）{returna*b；}12.}and：20.publicclassSubCalcextendsSuperCalc{21.publicstaticintmultiply（inta，intb）{22.intc=super.multiply（a，b）；23.returnc；24.}25.}and：30.SubCalcsc=newSubCalc（）；31.System.out.println（sc.multiply（3，4））；32.System.out.println（SubCalc.multiply（2，2））；Whatistheresult？（）

A.124

B.Thecoderunswithnooutput.

C.Anexceptionisthrownatruntime.

D.Compilationfailsbecauseofanerrorinline21.

E.Compilationfailsbecauseofanerrorinline22.

F.Compilationfailsbecauseofanerrorinline31.

publicclassFoo{publicinta；publicFoo（）{a=3；}publicvoidaddFive（）{a+=5；}}and：publicclassBarextendsFoo{publicinta；publicBar（）{a=8；}publicvoidaddFive（）{this.a+=5；}}invokedwith：Foofoo=newBar（）；foo.addFive（）；System.out.println（”Value：+foo.a）；Whatistheresult？（）

A.Value：3

B.Value：8

C.Value：13

D.Compilationfails.

E.Thecoderunswithnooutput.

F.Anexceptionisthrownatruntime.