面向对象编程基础习题及答案.docx
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面向对象编程基础习题及答案.docx
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面向对象编程基础习题及答案
面向对象编程基础习题及答案
PartI.ChoiceQuestions(1ptforeachquestion).
1.Toaddatobandstoreresultinb,youwrite(Note:
Javaiscase-sensitive)
A.b+=a;
B.a=b+a;
C.b=A+b;
D.a+=b;
2.TodeclareaconstantPI,youwrite
A.finalstaticPI=3.14159;
B.finalfloatPI=3.14159;
C.staticdoublePI=3.14159;
D.finaldoublePI=3.14159;
3.Toimprovereadabilityandmaintainability,youshoulddeclare_________insteadofusingliteralvaluessuchas3.14159.
A.variables
B.methods
C.constants
D.classes
4.Todeclareanintvariablexwithinitialvalue200,youwrite
A.intx=200L;
B.intx=200l;
C.intx=200;
D.intx=200.0;
5.Toassignadoublevariabledtoanintvariablex,youwrite
A.x=(long)d
B.x=(int)d;
C.x=d;
D.x=(float)d;
6.InJava,thewordtrueis________.
A.aJavakeyword
B.aBooleanliteral
C.sameasvalue1
D.sameasvalue0
7.WhichoftheBooleanexpressionsbelowhasincorrectsyntax?
A.(true)&&(3>4)
B.!
(x>0)&&(x>0)
C.(x>0)||(x<0)
D.(x!
=0)||(x=0)
8.Whichofthefollowingisthecorrectexpressionthatevaluatestotrueifthenumberxisbetween1and100orthenumberisnegative?
A.1 B.((x<100)&&(x>1))||(x<0) C.((x<100)&&(x>1))&&(x<0) D.(1>x>100)||(x<0) 9.Whichofthefollowingisthecorrectexpressionofcharactera? A.'a' B."a" C.'\000a' D.Noneoftheabove. 10.Whichofthefollowingstatementprintssmith\exam1\test.txt? A.System.out.println("smith\exam1\test.txt"); B.System.out.println("smith\\exam1\\test.txt"); C.System.out.println("smith\"exam1\"test.txt"); D.System.out.println("smith"\exam1"\test.txt"); 11.Supposeiisaninttypevariable.WhichofthefollowingstatementsdisplaythecharacterwhoseUnicodeisstoredinvariablei? A.System.out.println(i); B.System.out.println((char)i); C.System.out.println((int)i); D.System.out.println(i+""); 12.TheUnicodeof'a'is97.WhatistheUnicodefor'c'? A.96 B.97 C.98 D.99 13.Whichofthefollowingisaconstant,accordingtoJavanamingconventions? A.MAX_VALUE B.Test C.read D.ReadInt 14.Whichofthefollowingassignmentstatementsisillegal? A.floatf=-34; B.intt=23; C.shorts=10; D.floatf=34.0; 15.AJavastatementendswitha__________. A.comma(,) B.semicolon(;) C.period(.) D.closingbrace 16.TheassignmentoperatorinJavais__________. A.: = B.= C.== D.<- 17.Supposemandrareintegers.WhatisthecorrectJavaexpressionform/r^2toobtainafloatingpointresultvalue? (r^2denotesrraisedtothepowerof2). A.m/r*r B.m/(r*r) C.1.0*m/r*r D.1.0*m/(r*r) 18.Whichofthesedatatypesrequirestheleastamountofmemory? A.float B.double C.short D.byte 19.Whichofthefollowingoperatorshasthehighestprecedence? A.casting B.+ C.* D./ 20.Anintvariablecanhold__________. A.'x' B.93 C.98.3 D.true E.aandb 21.Whichofthefollowingassignmentstatementsiscorrecttoassigncharacter5toc? A.charc='5'; B.charc=5; C.charc="5"; D.charc="344"; 22.NotethattheUnicodeforcharacterAis65.Theexpression"A"+1evaluatesto________. A.66 B.B C.A1 D.Illegalexpression 23.ThenotequalcomparisonoperatorinJavais__________. A.<> B.! = C.! == D.^= 24.Ifyouattempttoaddanint,abyte,along,andadouble,theresultwillbea__________value. A.byte B.int; C.long; D.double; 25.Whatisthevalueof(double)5/2? A.2; B.2.5; C.3; D.2.0; 26.Whatisthevalueof(double)(5/2)? A.2; B.2.5; C.3; D.2.0; 27.Analyzethefollowingcode. publicclassTest{ publicstaticvoidmain(String[]args){ intmonth=09; System.out.println("monthis"+month); } } A.Theprogramdisplaysmonthis09 B.Theprogramdisplaysmonthis9 C.Theprogramdisplaysmonthis9.0 D.Theprogramhasasyntaxerror,because09isanincorrectliteralvalue. 28.Toassignadoublevariabledtoafloatvariablex,youwrite A.x=(long)d B.x=(int)d; C.x=d; D.x=(float)d; 29.whatisydisplayedinthefollowingcode? publicclassTest1{ publicstaticvoidmain(String[]args){ intx=1; inty=x=x+1; System.out.println("yis"+y); } } A.yis0. B.yis1becausexisassignedtoyfirst. C.yis2becausex+1isassignedtoxandthenxisassignedtoy. D.Theprogramhasasyntaxerrorsincexisredeclaredinthestatementinty=x=x+1. 30.Ifaprogramcompilesfine,butitterminatesabnormallyatruntime,thentheprogramsuffers__________. A.asyntaxerror B.aruntimeerror C.alogicerror 31.Supposex=0andy=0whatisxafterevaluatingtheexpression(y>0)&(1>x++). A.0 B.-1 C.1 32.Supposex=0andy=0whatisxafterevaluatingtheexpression(y>0)&&(1>x++). A.0 B.-1 C.1 33.SupposeyoudefineaJavaclassasfollows: publicclassTest{ } Inordertocompilethisclass,theclassshouldbestoredinafilenamed A.Test.class B.Test.doc C.Test.txt D.Test.java E.Anynamewithextension.java 34.ThecommandtocompileaclassinthefileTest.javais A.javaTest B.javaTest.java C.javacTest.java D.javacTest E.JAVACTest.java 35.WhichJDKcommandiscorrecttorunaJavaapplicationinByteCode.class? A.javaByteCode B.javaByteCode.class C.javacByteCode.java D.javacByteCode E.JAVACByteCode 36.Whatis1%2? A.0 B.1 C.2 37.Whatis"Welcome"+1+1*2? A.Welcome11*2 B.Welcome4 C.Welcome12 D.Welcome3 38.Whatistheprintoutofthefollowingcode: doublex=10.1; inty=(int)x; System.out.println("xis"+x+"andyis"+y); A.xis10andyis10 B.xis10.0andyis10.0 C.xis11andyis11 D.xis10.1andyis10 E.xis10.1andyis10.0 39.Whichofthefollowingcodedisplaystheareaofacircleiftheradiusispositive. A.if(radius! =0)System.out.println(radius*radius*Math.PI); B.if(radius>=0)System.out.println(radius*radius*Math.PI); C.if(radius>0)System.out.println(radius*radius*Math.PI); D.if(radius<=0)System.out.println(radius*radius*Math.PI); 40.Supposex=1,y=-1,andz=1.Whatistheprintoutofthefollowingstatement? if(x>0) if(y>0) System.out.println("x>0andy>0"); elseif(z>0) System.out.println("x<0andz>0"); A.x>0andy>0; B.x<0andz>0; C.x<0andz<0; D.noprintout. 41.Analyzethefollowingcode: booleaneven=false; if(even=true){ System.out.println("Itiseven! "); } A.Theprogramhasasyntaxerror. B.Theprogramhasaruntimeerror. C.Theprogramrunsfine,butdisplaysnothing. D.TheprogramrunsfineanddisplaysItiseven! . 42.Analyzethefollowingcode: //Enteraninteger StringnumString=JOptionPane.showInputDialog(null, "Enteranumber: ", "ExamInput", JOptionPane.QUESTION_MESSAGE); intnumber=Integer.parseInt(numString); if(number<=0) System.out.println(number); A.Theifstatementiswrong,becauseitdoesnothavetheelseclause; B.System.out.println(number);mustbeplacedinsidebraces; C.Ifnumberiszero,numberisdisplayed; D.Ifnumberispositive,numberisdisplayed. E.numberenteredfromthekeyboardcannotbenegative. 43.Analyzethefollowingcode. importjavax.swing.*; publicclassShowErrors{ publicstaticvoidmain(String[]args){ inti; intj; Strings=JOptionPane.showInputDialog(null, "Enteraninteger","Input", JOptionPane.QUESTION_MESSAGE); j=Integer.parseInt(s); i=(i+4); } } A.Theprogramcannotcompilebecausejisnotinitialized. B.Theprogramcannotcompilebecauseidoesnothaveaninitialvaluewhenitisusedini=i+4; C.Theprogramcompilesbuthasaruntimeerrorbecauseideosnothaveaninitialvaluewhenitisusedini=i+4; D.Theprogramcompilesandrunsfine. 44.Whatistheoutputofthefollowingcode: (Pleaseindentthestatementcorrectlyfirst.) intx=9,y=8,z=7; if(x>9) if(y>8) System.out.println("x>9andy>8"); elseif(z>=7) System.out.println("x<=9andz>=7"); else System.out.println("x<=9andz<7"); A.x>9andy>8; B.x<=9andz>=7; C.x<=9andz<7; D.Noneoftheabove. 45.Analyzethefollowingcode: StringnumString=JOptionPane.showInputDialog(null, "Enteranumber: ", "ExamInput", JOptionPane.QUESTION_MESSAGE); intnumber=Integer.parseInt(numString); if(number<=0) System.out.println(number); System.out.println(number); A.numberisalwaysprintedoutatleastonce; B.numberisprintedouttwiceifnumberiszero; C.numberisprintedouttwiceifnumberisnegative; D.numberisprintedoutonceifnumberispositive. E.Alloftheabove. 46.Whatisyafterthefollowingswitchstatement? intx=0; inty=0; switch(x+1){ case0: y=0; case1: y=1; default: y=-1 } A.1 B.-1 C.0 D.Noneoftheabove 47.Whatistheprintoutofthefollowingswitchstatement? charch='a'; switch(ch){ case'a': case'A': System.out.print(ch);break; case'b': case'B': System.out.print(ch);break; case'c': case'C': System.out.print(ch);break; case'd': case'D': System.out.print(ch); } A.abcd B.a C.aa D.ab E.abc 48.Analyzethefollowingcode. intx=0; inty=((x<100)&(x>0))? 1: -1; A.Thecodehasasyntaxerrorbecause&mustbe&&. B.ybecomes1afterthecodeisexecuted. C.ybecomes-1afterthecodeisexecuted. D.Noneoftheabove. 49.Whichofthefollowingisnotavalidbooleanexpression. A.(1 B.(x=1)||(x! =1) C.a,bareallcorrect D.a,bareallwrong 50.Whichofthefollowingexpressionisequivalentto(x>1
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