Module 7 集合和泛型.docx
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Module7集合和泛型
CopyrightTarenaCorporation,2008.Allrightsreserved
Module7-集合和泛型
一、选择题：
Question1
Given:
11.publicclassPerson{
12.privatename;
13.publicPerson（Stringname）{
14.this.name=name;
15.}
16.publicinthashCode（）{
17.return420;
18.}
19.}
Whichistrue?
A.ThetimetofindthevaluefromHashMapwithaPersonkeydepends
onthesizeofthemap.
B.DeletingaPersonkeyfromaHashMapwilldeleteallmapentriesfor
allkeysoftypePerson.
C.InsertingasecondPersonobjectintoaHashSetwillcausethefirst
Personobjecttoberemovedasaduplicate.
D.ThetimetodeterminewhetheraPersonobjectiscontainedina
HashSetisconstantanddoesNOTdependonthesizeofthemap.
Answer:
A
Question2
Given:
11.publicstaticCollectionget（）{
12.Collectionsorted=newLinkedList（）;
13.sorted.add（"B"）;sorted.add（"C"）;sorted.add（"A"）;
14.returnsorted;
15.}
16.publicstaticvoidmain（String[]args）{
17.for（Objectobj:
get（））{
18.System.out.print（obj+","）;
19.}
20.}
Whatistheresult?
A.A,B,C,
B.B,C,A,
C.Compilationfails.
D.Thecoderunswithnooutput.
E.Anexceptionisthrownatruntime.
Answer:
BCopyrightTarenaCorporation,2008.Allrightsreserved
Question3
Given:
1.importjava.util.*;
2.publicclassExample{
3.publicstaticvoidmain（String[]args）{
4.//insertcodehere
5.set.add（newinteger
（2））;
6.set.add（newinteger（l））;
7.System.out.println（set）;
8.}
9.}
Whichcode,insertedatline4,guaranteesthatthisprogramwill
output[1,2]?
A.Setset=newTreeSet（）;
B.Setset=newHashSet（）;
C.Setset=newSortedSet（）;
D.Listset=newSortedList（）;
E.Setset=newLinkedHashSet（）;
Answer:
A
Question4
Given:
1.importjava.util.*;
2.publicclassPQ{
3.publicstaticvoidmain（String[]args）{
4.PriorityQueuepq=newPriorityQueue（）;
5.pq.add（"carrot"）;
6.pq.add（"apple"）;
7.pq.add（"banana"）;
8.System.out.println（pq.poll（）+":
"+pq.peek（））;
9.}
10.}
Whatistheresult?
A.apple:
apple
B.carrot:
apple
C.apple:
banana
D.banana:
apple
E.carrot:
carrot
F.carrot:
banana
Answer:
C
Question5
Given:
1.importjava.util.*;CopyrightTarenaCorporation,2008.Allrightsreserved
2.publicclassWrappedString{
3.privateStrings;
4.publicWrappedString（Strings）{this.s=s;}
5.publicstaticvoidmain（String[]args）{
6.HashSet
7.WrappedStringws1=newWrappedString（"aardvark"）;
8.WrappedStringws2=newWrappedString（"aardvark"）;
9.Strings1=newString（"aardvark"）;
10.Strings2=newString（"aardvark"）;
11.hs.add（ws1）;hs.add（ws2）;hs.add（s1）;hs.add（s2）;
12.System.out.println（hs.size（））;}}
Whatistheresult?
A.0
B.1
C.2
D.3
E.4
F.Compilationfails.
G.Anexceptionisthrownatruntime.
Answer:
D
Question6
ClicktheExhibitbutton.
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.Thesetvariablecontainsonlythreeelementsfromthecoll
collection,andtheorderisguaranteedtobepreserved.
C.Thesetvariablecontainsallsixelementsfromthecoilcollection,
buttheorderisNOTguaranteedtobepreserved.
D.ThesetvariablecontainsonlythreeelementsfromthecoilCopyrightTarenaCorporation,2008.Allrightsreserved
collection,buttheorderisNOTguaranteedtobepreserved.
Answer:
D
Question7
Aprogrammerhasanalgorithmthatrequiresajava.util.Listthat
providesanefficientimplementationofadd（0,object）,butdoes
NOTneedtosupportquickrandomaccess.Whatsupportsthese
requirements?
A.java.util.Queue
B.java.util.ArrayList
C.java.util.LinearList
D.java.util.LinkedList
Answer:
D
Question8
ClicktheExhibitbutton.
1.importjava.util.*;
2.classKeyMaster{
3.publicinti;
4.publicKeyMaster（inti）{this.i=i;}
5.publicbooleanequals（Objecto）{returni==（（KeyMaster）o）.i;}
6.publicinthashCode（）{returni;}
7.}
8.publicclassMapIt{
9.publicstaticvoidmain（String[]args）{
10.Setset=newHashSet（）;
11.KeyMasterk1=newKeyMaster
（1）;
12.KeyMasterk2=newKeyMaster
（2）;
13.set.add（k1）;set.add（k1）;
14.set.add（k2）;set.add（k2）;
15.System.out.print（set.size（）+":
"）;
16.k2.i=1;
17.System.out.print（set.size（）+":
"）;
18.set.remove（k1）;
19.System.out.print（set.size（）+":
"）;
20.set.remove（k2）;
21.System.out.print（set.size（））;
22.}
23.}
Whatistheresult?
A.4:
4:
2:
2
B.4:
4:
3:
2
C.2:
2:
1:
0
D.2:
2:
0:
0CopyrightTarenaCorporation,2008.Allrightsreserved
E.2:
1:
0:
0
F.2:
2:
1:
1
G.4:
3:
2:
1
Answer:
F
Question9
Given:
11.publicstaticvoidappend（Listlist）{list.add（"0042"）;}
12.publicstaticvoidmain（String[]args）{
13.ListintList=newArrayList（）;
14.append（intList）;
15.System.out.println（intList.get（0））;
16.}
‘Whatistheresult?
A.42
B.0042
C.Anexceptionisthrownatruntime.
D.Compilationfailsbecauseofanerrorinline13.
E.Compilationfailsbecauseofanerrorinline14.
Answer:
B
Question10
Given:
int[]myArray=newint[]{1,2,3,4,5};
Whatallowsyoutocreatealistfromthisarray?
A.ListmyList=myArray.asList（）;
B.ListmyList=Arrays.asList（myArray）;
C.ListmyList=newArrayList（myArray）;
D.ListmyList=Collections.fromArray（myArray）;
Answer:
B
Question11
Given:
34.HashMapprops=newHashMap（）;
35.props.put（"key45","somevalue"）;
36.props.put（"key12","someothervalue"）;
37.props.put（"key39","yetanothervalue"）;
38.Sets=props.keySet（）;
39.//insertcodehere
What,insertedatline39,willsortthekeysinthepropsHashMap?
A.Arrays.sort（s）;
B.s=newTreeSet（s）;
C.Collections.sort（s）;CopyrightTarenaCorporation,2008.Allrightsreserved
D.s=newSortedSet（s）;
Answer:
B
Question12
Given:
11.publicclassPerson{
12.privateStringname,comment;
13.privateintage;
14.publicPerson（Stringn,inta,Stringc）{
15.name=n;age=a;comment=c;
16.}
17.publicbooleanequals（Objecto）{
18.if（!
（oinstanceofPerson））returnfalse;
19,Personp=（Person）o;
20.returnage==p.age&&name.equals（p.name）;
21.}
22.}
WhatistheappropriatedefinitionofthehashCodemethodinclass
Person?
A.returnsuper.hashCode（）;
B.returnname.hashCode（）+age*7;
C.returnname.hashCode（）+comment.hashCode（）/2;
D.returnname.hashCode（）+comment.hashCode（）/2-age*3;
Answer:
B
Question13
Given:
11.publicclassKey{
12.privatelongid1;
13.privatelong1d2;
14.
15.//classKeymethods
16.}
AprogrammerisdevelopingaclassKey,thatwillbeusedasakeyin
astandardjava.util.HashMap.Whichtwomethodsshouldbe
overriddentoassurethatKeyworkscorrectlyasakey?
（Choosetwo.）
A.publicinthashCode（）
B.publicbooleanequals（Keyk）
C.publicintcompareTo（Objecto）
D.publicbooleanequals（Objecto）
E.publicbooleancompareTo（Keyk）
Answer:
ADCopyrightTarenaCorporation,2008.Allrightsreserved
Question14
Given:
11.publicclassPerson{
12.privatename;
13.publicPerson（Stringname）{
14.this.name=name;
15.}
16.publicbooleanequals（Objecto）{
17.if（!
oinstanceofPerson）returnfalse;
18.Personp=（Person）o;
19.returnp.name.equals（this.name）;
20.}
21.}
Whichistrue?
A.CompilationfailsbecausethehashCodemethodisnotoverridden.
B.AHashSetcouldcontainmultiplePersonobjectswiththesame
name.
C.AllPersonobjectswillhavethesamehashcodebecausethe
hashCodemethodisnotoverridden.
D.IfaHashSetcontainsmorethanonePersonobjectwith
name="Fred",thenremovinganotherPerson,alsowithname="Fred",
willremovethemall.
Answer:
B
Question15
Given:
1.publicclassPerson{
2.privateStringname;
3.publicPerson（Stringname）{this.name=name;}
4.publicbooleanequals（Personp）{
5.returnp.name.equals（this.name）;
6.}
7.}
Whichistrue?
A.TheequalsmethoddoesNOTproperlyoverridetheObject.equals
method.
B.Compilationfailsbecausetheprivateattributep.namecannotbe
accessedinline5.
C.Toworkcorrectlywithhash-baseddatastructures,thisclassmust
alsoimplementthehashCodemethod.
D.WhenaddingPersonobjectstoajava.util.Setcollection,theequals
methodinline4willpreventduplicates.
Answer:
ACopyrightTarenaCorporation,2008.Allrightsreserved
Question16
WhichtwostatementsaretrueaboutthehashCodemethod?
（Choose
two.）
A.ThehashCodemethodforagivenclasscanbeusedtotestfor
objectequalityandobjectinequalityforthatclass.
B.ThehashCodemethodisusedbythejava.util.SortedSetcollection
classtoordertheelementswithinthatset.
C.ThehashCodemethodforagivenclasscanbeusedtotestfor
objectinequality,butNOTobjectequality,forthatclass.
D.Theonlyimportantcharacteristicofthevaluesreturnedbya
hashCodemethodisthatthedistributionofvaluesmustfollowa
Gaussiandistribution.
E.ThehashCodemethodisusedbythejava.util.HashSetcollection
classtogrouptheelementswithinthatsetintohashbucketsfor
swiftretrieval.
Answer:
CE
Question17
Given:
enumExample{ONE,TWO,THREE}
Whichistrue?
A.Theexpressions（ONE==ONE）andONE.equals（ONE）areboth
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