OCJP题库详解.docx
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OCJP题库详解.docx
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OCJP题库详解
SCJP6.0
AlbertChu
1.Whichtwostatementsaretrue?
(Choosetwo.)
A.Line35willnotcompile.
B.Line36willnotcompile.
C.Line37willnotcompile.
D.Line38willnotcompile.
Answer:
AD
Analyses:
String$name=”500”;
Int_s=2;
Doublef=1;//errordoublea=1//true
Doublef=1.2//truedoublea=1.2//true
Caution:
符号只有$和_可以(定义后不能再使用),其它符号会显示错误(无文件)
2.Whatistheoutput?
A.42
B.420
C.462
D.42042
E.Compilationfails.
F.Anexceptionisthrownatruntime.
Answers:
D
Caution:
字符串可以相加
3.Whatistheresult?
A.2
B.3
C.12
D.23
E.123
F.Compilationfails.
G.Anexceptionisthrownatruntime.
Answers:
D
Analyses:
if(1==3)if(1==3){
System.out.println(“1”)System.out.println(“1”)
System.out.println(“2”)System.out.println(“2”)
System.out.println(“3”)}System.out.println(“3”)
//output//output
23
3
Caution:
if()else如果无{}默认if()下面第一个表达式
4.Whatistheresultwhenthego()methodisinvoked?
A.00
B.0001
C.000120
D.00012021
E.Compilationfails.
F.Anexceptionisthrownatruntime.
Answers:
C
Analyses:
(1)当x=0时,y=0,o=00;y=1,o=0001;
(2)当x=1时,y=0,break(跳出for循环);y=1,break(跳出for循环);
(3)当x=2时,y=0,o=000120;y=1,breakz跳出两层for循环;
输出o=000120
Caution:
break是跳出一层for循环,而使用标签breakz能跳出两层for循环.
5.Whatistheresult?
A.5,6
B.5,5
C.6,5
D.6,6
Answers:
B
Analyses:
y=9,x=1;y=8,x=2;y=7,x=3;y=6,x=4;y=5,x=5;
输出5,5
Caution:
++i,先自增1再使用;i++,先使用再自增1.
6.Whatistheresult?
A.23
B.234
C.235
D.2345
E.2357
F.23457
G.Compilationfails.
Answers:
G
Analyses:
程序有错误,不能运行,因为标签Z和for循环之间还有表达式。
Caution:
标签名必须紧挨for循环,break跳出for循环。
7.Whatistheresult?
A.2B.24C.234D.246E.2346F.Compilationfails.
Answers:
B
Analyses:
当x=2时,o=2;当x=3时,跳过本次循环继续;当x=4时,o=24;
当x=5时,跳出整个循环。
输出o=24
Caution:
break跳出整个循环;continue跳过本次循环继续。
8.Whatistheresult?
A.1B.2C.12D.Compilationfails.E.Nooutputisproduced.F.Anexceptionisthrownatruntime.
Answers:
E
Analyses:
if((tail>distance)^((story*2)==tail))即1^1结果0
if((distance+1!
=tail)^((story*2)==distance))即0^0结果0
Caution:
1^1结果00^0结果01^0结果10^1结果1
9.Whatistheresult?
A.Compilationfails.
B.Anexceptionisthrownatruntime.
C.Thevariablefirstissettonull.
D.Thevariablefirstissettoelements[0].
Answers:
D
Analyses:
(elements.length>0)值为真,执行elements[0]
即将for字符串赋给first
Caution:
三元操作符x X: Y 10.Whatistheresult? A.2-1B.2-4C.2-5D.3-1E.3-4F.3-5G.Compilationfails.H.Anexceptionisthrownatruntime. Answers: C Analyses: Caution: 幻灯片12 011 E 1.classAlligator{ 2.publicstaticvoidmain(String[]args){ 3.int[]x[]={{1,2},{3,4,5},{6,7,8,9}}; 4.int[][]y=x; 5.System.out.print(y[2][1]); 6.} 7.} Whatistheresult? 幻灯片13 012 幻灯片14 013 D 1.publicclassBarn{ 2.publicstaticvoidmain(String[]args){ 3.newBarn.go("hi",1); 4.newBarn.go("hi","world",2); 5.} 6.publicvoidgo(String...y,intx){ 7.System.out.print(y[y.length-1]+""); 8.} 9.} Whatistheresult? 幻灯片15 014 D 11.classPerson{ 12.Stringname="Noname"; 13.publicPerson(Stringnm){name=nm;} 14.} 15. 16.classEmployeeextendsPerson{ 17.StringempID="0000"; 18.publicEmployee(Stringid){empID=id;} 19.} 20. 21.classEmployeeTest{ 22.publicstaticvoidmain(String[]args){ 23.Employeee=newEmployee("4321"); 24.System.out.println(e.empID); 25.} 26.} Whatistheresult? 幻灯片16 015 D 11.classMud{ 12.//insertcodehere 13.System.out.println("hi"); 14.} 15.} Andthefollowingfivefragments: publicstaticvoidmain(String...a){//r publicstaticvoidmain(String.*a){ publicstaticvoidmain(String...a){//r publicstaticvoidmain(String[]...a){//r publicstaticvoidmain(String...[]a){ Howmanyofthecodefragments, insertedindependentlyatline12,compile? 幻灯片17 016 5.classAtom{ 6.Atom(){System.out.print("atom");} 7.} 8.classRockextendsAtom{ 9.Rock(Stringtype){System.out.print(type);} 10.} 11.publicclassMountainextendsRock{ 12.Mountain(){ 13.super("granite"); 14.newRock("granite"); 15.} 16.publicstaticvoidmain(String[]a){newMountain();} 17.} Whatistheresult? F 幻灯片18 017 ACEFG 1.publicclassBlip{ 2.protectedintblipvert(intx){return0;} 3.} 4.classVertextendsBlip{ 5.//insertcodehere 6.} Whichfivemethods,insertedindependentlyatline5, willcompile? (Choosefive.) 幻灯片19 018 CD 1.classSuper{ 2.privateinta; 3.protectedSuper(inta){this.a=a;} 4.} ... 11.classSubextendsSuper{ 12.publicSub(inta){super(a);} 13.publicSub(){this.a=5;} 14.} Whichtwo,independently,willallowSubtocompile? (Choosetwo.) 幻灯片20 019 D WhichManclassproperlyrepresentstherelationship "ManhasabestfriendwhoisaDog"? A.classManextendsDog{} B.classManimplementsDog{} C.classMan{privateBestFrienddog;} D.classMan{privateDogbestFriend;} E.classMan{privateDog F.classMan{privateBestFriend 幻灯片21 020 AD AteamofprogrammersisreviewingaproposedAPIforanewutilityclass. Aftersomediscussion,theyrealizethattheycanreducethenumberofmethodsintheAPIwithoutlosinganyfunctionality. Iftheyimplementthenewdesign,whichtwoOOprincipleswilltheybepromoting? A.Loosercoupling B.Tightercoupling C.Lowercohesion D.Highercohesion E.Weakerencapsulation F.Strongerencapsulation 幻灯片22 021 B 1.classBatman{ 2.intsquares=81; 3.publicstaticvoidmain(String[]args){ 4.newBatman().go(); 5.} 6.voidgo(){ 7.incr(++squares); 8.System.out.println(squares); 9.} 10.voidincr(intsquares){squares+=10;} 11.} Whatistheresult? 幻灯片23 022 D 1.classPass{ 2.publicstaticvoidmain(String[]args){ 3.intx=5; 4.Passp=newPass(); 5.p.doStuff(x); 6.System.out.print("mainx="+x); 7.} 8.voiddoStuff(intx){ 9.System.out.println("doStuffx="+x++); 10.} 11.} Whatistheresult? 幻灯片24 023 BC Acompanyhasabusinessapplicationthatprovidesitsuserswithmanydifferentreports: receivablesreports,payablesreports,revenueprojects,andsoon. Thecompanyhasjustpurchasedsomenew,state-of-the-art, wirelessprinters,andaprogrammerhasbeenassignedthetaskofenhancingallofthereportstousenotonlythecompany'soldprinters,butthenewwirelessprintersaswell. Whentheprogrammerstartslookingintotheapplication,theprogrammerdiscoversthatbecauseofthedesignoftheapplication,itisnecessarytomakechangestoeachreporttosupportthenewprinters.Whichtwodesignconceptsmostlikelyexplainthesituation? (Choosetwo.) 幻灯片25 024 B AcompanythatmakesComputerAssistedDesign(CAD)softwarehas,withinitsapplicationsomeutilityclassesthatareusedtoperform3Drenderingtasks. Thecompany'schiefscientisthasjustimprovedtheperformanceofoneoftheutilityclasses'keyrenderingalgorithms,andhasassignedaprogrammertoreplacetheoldalgorithmwiththenewalgorithm. Whentheprogrammerbeginsresearchingtheutilityclasses,sheishappytodiscoverthatthealgorithmtobereplacedexistsinonlyoneclass.Theprogrammerreviewsthatclass'sAPI,andreplacestheoldalgorithmwiththenewalgorithm,beingcarefulthatherchangesadherestrictlytotheclass'sAPI.Oncetestinghasbegun,theprogrammerdiscoversthatotherclassesthatusetheclassshechangedarenolongerworkingproperly. Whatdesignflawismostlikelythecauseoftherenewbugs? 幻灯片26 025 A 1.classClassA{ 2.publicintnumberOfInstances; 3.protectedClassA(intnumberOfInstances){ 4.this.numberOfInstances=numberOfInstances; 5.} 6.} 7.classExtendedAextendsClassA{ 8.privateExtendedA(intnumberOfInstances){ 9.super(numberOfInstances); 10.} 11.publicstaticvoidmain(String[]args){ 12.ExtendedAext=newExtendedA(420); 13.System.out.print(ext.numberOfInstances); 14.} 15.} Whatistheresult? 幻灯片27 026 BCF 10.interfaceJumper{publicvoidjump();} ... 20.classAnimal{} ... 30.classDogextendsAnimal{ 31.Tailtail; 32.} ... 40.classBeagleextendsDogimplementsJumper{ 41.publicvoidjump(){} 42.} ... 50.classCatimplementsJumper{ 51.publicvoidjump(){} 52.} Whichthreearetrue? (Choosethree.) 幻灯片28 027 BCE 10.classOne{ 11.voidfoo(){} 12.} 13.classTwoextendsOne{ 14.//insertmethodhere 15.} Whichthreemethods,insertedindividuallyatline14,willcorrectlycompleteclassTwo? (Choosethree.) 幻灯片29 028 C 1.classX{ 2.X(){System.out.print (1);} 3.X(intx){ 4.this(); 5.System.out.print (2); 6.} 7.} 8.publicclassYextendsX{ 9.Y(){ 10.super(6); 11.System.out.print(3); 12.} 13.Y(inty){ 14.this(); 15.System.out.println(4); 16.} 17.publicstaticvoidmain(String[]a){newY(5);} 18.} Whatistheresult? 幻灯片30 029 C ●1.publicclassA{ ●2.publicvoiddoit(){ ●3.} ●4.publicStringdoit(){ ●5.return"a"; ●6.} ●7.publicdoubledoit(intx){ ●8.return1.0; ●9.} ●10.} ●Whatistheresult? 幻灯片31 030 A 1.publicclassSimpleCalc{ 2.publicintvalue; 3.publicvoidcalculate(){value+=7;} 4.} And: 1.publicclassMultiCalcextendsSimpleCalc{ 2.publicvoidcalculate(){value-=3;} 3.publicvoidcalculate(intmultiplier){ 4.calculate(); 5.super.calculate(); 6.value*=multiplier; 7.} 8.publicstaticvoidmain(String[]args){ 9.MultiCalccalculator=newMultiCalc(); 10.calculator.calculate (2); 11.System.out.println("Valueis: "+c
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