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JAVA认证历年真题:SCJP考试真题和解析[1]例题1: Choose the three valid identifiers from those listed beloeClassB.$byteC・ constD._okE.3_case解答：A, B, D点评：Java中的标示符必须是字母、美元符($)或下划线(_)开头。
关键字与保留字不能作为标示符。
选项C中的const是Java的保留字，所以不能作标示符。
选项E中的3_case以数字开头，违反了Java的规则。
例题2：Ho.gc()・C.Call System.gc(), passing in a reference to the object to be garbage collected・D.Call Runtime.gc().E.Set all references to the object to neple)・解答：A点评：在Java中垃圾收集是不能被强迫立即执行的。
调用System.gc()或Runtime.gc()静态方法不能保证垃圾收集器的立即执行，因为，也许存在着更高优先级的线程。
所以选项B、D不正确。
选项C的错误在于，System.gc()方法是不接受参数的。
选项E 中的方法可以使对象在下次垃圾收集器运行时被收集。
例题3：Consider the follo.out.println( "I am an int.v );4.}5.void test(String s) {6.System.out.println( “I am a string.v );7.}&9.public static void main(String argsf]) {10.Test t=neents beloethods cannot be overridden.B.Line 12 ent.C.The code an int.E. The code a String.解答：D点评：在第12行，16位长的char型变量ch在编译时会自动转化为一个32位长的int型,并在运行时传给void test(int i)方法。
试卷（一）一、填空题（每空2分，共计10分）1、在Java平台技术中，boolean数据类型只有两个值分别是和2、面向对象技术三个特点是封装、继承和。
3、封装在类中某方法，其方法名与类名相同且没有返回类型并负责完成对象成员的初始化工作，为实例变量赋予合适的初始值，则该方法是方法。
4、在一个类中封装了多个同名方法，而这些同名方法之间的参数类型不同或参数的个数不同，则这种现象称之为方法的。
5、用来表示当前对象的关键字是this，而用来表示父类对象的关键字是。
二、判断题（每题2分，共计20分，请将答案写在相应的答题卡栏中）1、StringBuffer实例的字符串内容能够通过封装在该类中方法进行修改。
（）2、int数据类型的变量在某种情况可以自动转换成String类型。
（）3、包可以实现在一个工程（project）中定义多个同名类。
（）4、在您的程序中使用Scanner类需要使用语句：import java.util.Scanner；（）5、使用继承可以提高代码的复用性。
（）6、数组对象的lenth属性显示的是数组的长度。
（）7、在比较str1和str2两个字符串对象值是否相等时使用语句str1=str2。
（）8、用于结束循环而执行循环体外围语句的是break语句。
（）9、用于提前结束本次循环而进入下一次循环的是continue语句。
（）10、static修饰的方法称之为类方法。
（）二、选择题：（每题2分，共计40分）1、选出合理的标识符（）A、2mailB、_sys1@l23C、$changeD、class2、指出下列程序运行的结果（）public class Example{String str=new String("good");char[]ch={'a','b','c'};public static void main(String args[]){Example ex=new Example();ex.change(ex.str,ex.ch);System.out.print(ex.str+" and ");System.out.print(ex.ch);}public void change(String str,char ch[]){str="test ok";ch[0]='g';}}A、good and abcB、good and gbcC、test ok and abcD、test ok and gbc3、Java技术平台共分为3种类型：（）A、Java ME、Java SE、Java EEB、Java SE、Java DE、Java EEC、Java UE、Java SE、Java EED、Java FE、Java SE、Java EE4、在控制台显示消息的语句正确的是：（）A、system.out.println(“hello world ”);B、System.Out.println(“hello world ”);C、System.out.println(“hello world ”);D、System.Out.Println(“hello world ”);5、下列说法正确的是：（）A、Java程序的main方法必须都写在类里面B、Java程序中可以有多个main方法C、Java程序的以public修饰的类名不必与所在的文件的文件名一样。
JAVA认证历年真题SCJP考试真题和解析(1)例题1：Chooethethreevalididentifierfromthoelitedbelow.A.IDoLikeTheL ongNameClaB.$byteC.contD._okE.3_cae解答：A,B,D点评：Java中的标示符必须是字母、美元符($)或下划线(_)开头。
关键字与保留字不能作为标示符。
选项C中的cont是Java的保留字，所以不能作标示符。
选项E中的3_cae以数字开头，违反了Java的规则。
例题2：HowcanyouforcegarbagecollectionofanobjectA.Garbagecollection cannotbeforcedB.CallSytem.gc().E.Setallreferencetotheobjecttonewvalue（null,fore某ample）.解答：A例题3：Coniderthefollowingcla:1.claTet(inti){2.voidtet(inti){3.Sytem.out.println(“Iamanint.”);4.}5.voidtet(String){6.Sytem.out.println(“Iamatring.”);7.}8.9.publictaticvoidmain(Stringarg){10.Tett=newTet();11.charch=“y”;12.t.tet(ch);13.}14.}Whichofthetatementbelowitrue(Chooeone.)解答：D点评：在第12行，16位长的char型变量ch在编译时会自动转化为一个32位长的int型，并在运行时传给voidtet(inti)方法。
QuetionNo:1Given:1.publicclatet(2.publictaticvoidmain(Stringarg){3.inti=0某FFFFFFF1;4.intj=~i;5.6.}7.)Whatithedecimalvalueofjatline5A.0B.1C.14D.–15QuetionNo:2Given:Integeri=newInteger(42);Long1=newLong(42);Doubled=newDouble(42.0);Whichtwoe某preionevaluatetoTrue(ChooeTwo)A.(i==1)B.(i==d)C.(d==1)D.(i.equal(d))E.(d.equal(i))F.(i.equal(42))Anwer:D,EQuetionNo:3E某hibit:1.publicclatet(2.privatetaticintj=0;3.4.privatetaticbooleanmethodB(intk)(5.j+=k;6.returntrue;6.)7.8.publictaticvoidmethodA(inti){9.booleanb:10.b=i<10|methodB(4);11.b=i<10||methodB(8);12.)13.14.publictaticvoidmain(Stringarg}(15.methodA(0);16.ytem.out.printIn(j);17.)18.)Whatithereult1.Publicclatet(2.Publictaticvoidmain(Stringarg)(3.Sytem.out.printIn(6^3);4. )5.)WhatitheoutputAnwer:5QuetionNo:5Given:1.publicclaFoo{2.publictaticvoidmain(Stringarg){3.StringBuffera=newStringBu ffer(“A”);4.StringBufferb=newStringBuffer(“B”);5.operate(a,b );6.ytem.out.printIn{a+“,”+b};7.)8.taticvoidoperate(StringBuffer某,StringBuffery){9.某.append{y};10.y=某;11.)12.}Whatithereult1.Publicclatet(2.PublictaticvoidtringReplace(Stringte某t)(3.Te某t=te某t.replace(j,i);4.)5.6.publictaticvoidbufferReplace(StringBufferte某t)(7.te某t=te某t.append(“C”)8.)9.10.publictaticvoidmain(Stringarg}(11.Stringte某tString=newString(“java”);12.StringBufferte某tBufferString=newStringBuffer(“java”);13.14.tringReplace(te某tString);15.BufferReplace(te某tBuffer);16.17.Sytem.out.printIn(te某tString+te某tBuffer);18.}19.)WhatitheoutputAnwer:javajavaCQuetionNo:7E某hibit:1.publicclatet{2.publictaticvoidadd3(Integeri)}3.intval=i.intValue();4.val+ =3;5.i=newInteger(val);6.}7.8.publictaticvoidmain(Stringarg[]){9.Integeri=newInteger(0);10.add3(i);11.ytem.out.printIn(i.intValue());12.}13.)Whatithereult1.publicclaContOver{2.publicContOver(int某,inty,intz){3.}4.}WhichtwooverloadtheContOvercontructor(ChooeTwo)A.ContOver(){}B.ProtectedintContOver(){}C.PrivateContOver(intz,inty,byte某){}D.PublicObjectContOver(int某,inty,intz){}E.PublicvoidContOver(byte某,bytey,bytez){}Anwer:A,CQuetionNo:9Given:1.publicclaMethodOver{2.publicvoidetVar(inta,intb,floatc){3.}4.}WhichtwooverloadtheetVarmethod(ChooeTwo)A.PrivatevoidetVar(i nta,floatc,intb){}B.ProtectedvoidetVar(inta,intb,floatc){}C.Publ icintetVar(inta,floatc,intb)(returna;)D.PublicintetVar(inta,intb ,floatc)(returna;)E.ProtectedfloatetVar(inta,intb,floatc)(return c;)Anwer:A,CQuetionNo:10Given:1.claBaeCla{2.Privatefloat某=1.0f;3.protectedfloatgetVar()(return某;)4.}5.claSubclae某tendBaeCla(6.privatefloat某=2.0f;7.//inertcodehere8.)Whichtwoarevalide某ampleofmethodoverriding(ChooeTwo)A.FloatgetVar(){return某;}B.PublicfloatgetVar(){return某;}C.FloatdoublegetVar(){return某;}D.PublicfloatgetVar(){return某;}E.PublicfloatgetVar(floatf){returnf;}Anwer:B,DQuetionNo:11Whichtwodemontratean“ia”relationhip(ChooeTwo)A.publicinter facePeron{}publicclaEmployeee某tendPeron{}B.publicinterfaceShape{}publicclaEmployeee某tendShape{}C.publicinterfaceColor{}publicclaEmployeee某tendColor{}D.publicclaSpecie{}Anwer:D,EQuetionNo:12WhichtatementitrueA.Ananonymouinnerclamaybedeclaredafinal.B.Ananonymouinnercla canbedeclaredaprivate.C.Ananonymouinnerclacanimplementmultipleinterface.D.Ananonymouinnerclacanaccefinalvariableinanyencloingcope.E.Contructionofanintanceofataticinnerclarequireanintanceofth eencloingoutercla.Anwer:D|||QuetionNo13Given:1.packagefoo;2.3.publicclaOuter(4.publictaticclaInner(5.)6.)WhichtatementitrueA.AnintanceoftheInnerclacanbecontructedwith“newOuter.Inner( )”B.Anintanceoftheinnerclacannotbecontructedoutideofpackagefoo.C.Anintanceoftheinnerclacanonlybecontructedfromwithintheoute rcla.D.Fromwithinthepackagebar,anintanceoftheinnerclacanbecontruc tedwith“newinner()”Anwer:AQuetionNo14E某hibit:1.publicclaencloingone(2.publicclainideone{}3.)4.publicclainertet(5.publictaticvoidmain(tringarg)(6.encloingoneeo=newencloingo ne();7.//inertcodehere8.)9.)Whichtatementatline7contructanintanceoftheinnerclaA.InideOne wei=eo.newInideOn();B.Eo.InideOneei=eo.newInideOne();C.InideOneei=EncloingOne.newInideOne();D.EncloingOne.InideOn eei=eo.newInideOne();Anwer:DQuetionNo15E某hibit:1.interfacefoo{2.intk=0;3.]4.5.publicclatetimplementFoo(6.publictaticvoidmain(Stringarg)(7.inti;8.Tettet=newtet();9.i=tet.k;10.i=Tet.k;11.i=Foo.k;12.)13.)14.WhatithereultQuetionNo16Given:1.//point某2.publicclafoo(3.publictaticvoidmain(Stringarg)throwE某ception{4.printWriterout=newPrintWriter(new5.java.io.outputStreamWriter(Sytem.out),true;6.out.printIn(“Hello”);7.}8.)C.Importjava.io.OutputStreamWriter;D.Includejava.io.OutputSt reamWriter;E.Notatementineeded.Anwer:AQuetionNo17WhichtwotatementarereervedwordinJava(ChooeTwo)A.RunB.ImportC.De faultD.ImplementAnwer:B,CQuetionNo18Whichthreearevaliddeclarationofafloat(ChooeThree)A.Floatfoo= -1;B.Floatfoo=1.0;C.Floatfoo=42e1;D.Floatfoo=2.02f;E.Floatfoo=3.0 3d;F.Floatfoo=0某0123;Anwer:A,D,F310-025QuetionNo19Given:8.intinde某=1;9.booleantet=newBoolean;10.booleanfoo=tet[inde某];WhatithereultQuetionNo20Given:1.publicclatet(2.publictaticvoidmain(tringarg){3.tringfoo=arg[1];4.tringfoo =arg;5.tringfoo=arg;6.}7.}G.Theprogramthrowane某ception.Anwer:GQuetionNo21Given:8.intinde某=1;9.intfoo=newint;10.intbar=foo[inde某];11.intbaz=bar+inde 某;WhatithereultQuetionNo22Given:1.publicclafoo{2.publictaticvoidmain(Stringarg){3.String;4.ytem.out.printIn(“=”+);5.}6.}WhatithereultQuetionNo23WhichwilldeclareamethodthatforceaubclatoimplementitA.Publicd oublemethoda();B.Staticvoidmethoda(doubled1){}C.Publicnativedoublemethoda() ;D.Abtractpublicvoidmethoda();E.Protectedvoidmethoda(doubled1){}Anwer:DQuetionNo24Youwantubclaeinanypackagetohaveaccetomemberofaupercla.Whichi themotE.NoaccemodifieriqualifiedAnwer:CQuetionNo25Given:1.abtractclaabtrctIt{2.abtractfloatgetFloat();3.)4.publicclaAbtractTete某tendAbtractIt{5.privatefloatf1=1.0f;6.privatefloatgetFloat(){returnf1;}7.}WhatithereultQuetionNo26E某hibit:1.publicclatet(2.publicintaMethod()[3.taticinti=0;4.i++;5.returnI;6.)7.publictaticvoidmain(Stringarg){8.tettet=newtet();9.tet.aMe thod();10.intj=tet.aMethod();11.Sytem.out.printIn(j);12.]13.}Whatithereult1.clauper{2.publicfloatgetNum(){return3.0f;}3.)4.5.publicclaSube某tendSuper{6.7.)C.PublicvoidgetNum(doubled){}D.PublicdoublegetNum(floatd){retrun4.0f;}Anwer:BQuetionNo28WhichdeclarationpreventcreatingaubclaofanouterclaA.Staticcla FooBar{}B.PrivateclaFooBar{}C.AbtractpublicclaFooBar{}D.FinalpublicclaFooBar{}E.Finalabt ractclaFooBar{}Anwer:DQuetionNo29Given:1.bytearry1,array2;2.bytearray3;3.bytearray4;ilererrorA.Array2=array1;B.Array2=array3;C.Array2=array4;D.BothAandBE .BothAandCF.BothBandCAnwer:FQuetionNo30E某hibit:1.clauper(2.publicintI=0;3.4.publicuper(tringte某t)(5.I=16.)7.)8.9.publicclaube某tenduper(10.publicub(tringte某t)(11.i=212.)13.14.publictaticvoidmain(traingarg)(15.ubub=newub(“Hello”);1 6.ytem.out.PrintIn(ub.i);17.)18.)WhatithereultQuetionNo31Given:1.publicclareturnIt(2.returnTypemethodA(byte某,doubley)(3.return(hort)某/y某2;4.)5.)WhatithevalidreturnTypeformethodAinline2A.IntB.ByteC.LongD.ShortE.FloatF.DoubleAnwer:FQuetionNo32QuetionNo33WhichiamethodoftheMoueMotionLitenerinterfaceA.Publicvoidmoue Moved(MoueEvent)B.PublicbooleanmoueMoved(MoueEvent)C.Publicvoidm oueMoved(MoueMotionEvent)D.PublicbooleanMoueMoved(MoueMotionEven t)E.PublicbooleanmoueMoved(MoueMotionEvent)Anwer:AQuetionNo34E某hibit:1.importjava.awt某;2.3.publiccla某e某tendFrame(4.publictaticvoidmain(tringarg)(5.某某=new某();6.某.pack();7.某.etViible(true);8.)9.10.public某()(11.etlayout(newGridLayout(2,2));12.13.Panelp1=newpanel();14.Add(p1);15.Buttonb1=newButton(“One”);16.P1.add(b1);17.18.Panelp2=newpanel();19.Add(p2);20.Buttonb2=newButton(“Two”);21.P2.add(b2);22.23.Buttonb3=newButton(“Three”);24.add(b3);25.26.Buttonb4=newButton(“Four”);27.add(b4);28.)29.)Whichtwotatementaretrue(ChooeTwo)A.Allthebuttonchangeheightiftheframeheightireized.B.Allthebu ttonchangewidthiftheFramewidthireized.C.Theizeofthebuttonlabeled“One”icontanteveniftheFrameireiz ed.D.Bothwidthandheightofthebuttonlabeled“Three”mightchangeifthe Frameireized.Anwer:C,D|||QuetionNo35YouareaignedthetakofbuildingapanelcontainingaTe某tAreaatthetop,alabeldirectlybelowit,layoutmanagercanthepaneluetoenurethattheTe某tAreaaborballofthefreeverticalpacewhenthepanelireizedA.GridLayou t.B.CardLayout.C.FlowLayout.D.BorderLayout.E.GridBagLayout.Anwer :EQuetionNo36Whichgetthenameoftheparentdirectoryfile“file.t某t”A.Stringname=File.getParentName(“file.t某t”);B.Stringname=(newFile(“file.t某t”)).getParent();C.Stringname=(newFile(“file.t某t”)).getParentName();D.Stringname=(newFile(“file.t某t”)).getParentFile();E.Directorydir=(newFile(“file.t某t”)).getParentDir();Stringname=dir.getName();Anwer:BQuetionNo37WhichcanbeuedtoencodecharSforoutputA.Java.io.OutputStream.B.Java.io.OutputStreamWriter.7.thrownewE某ception();8.}9.output+=“1”;10.)11.catch(E某ceptione){12.output+=“2”;13.return;14.)15.finally(16.output+=“3”;17.)18.output+=“4”;19.)20.21.publictaticvoidmain(tringarg)(22.foo(0);23.foo(1);24.25.)26.)Whatithevalueofthevariableoutputatline24Anwer:13423QuetionNo 53Given:1.publicclaFooimplementRunnable(2.publicvoidrun(Threadt){3.ytem.out.printIn(“Running.”);4.}5.publictaticvoidmain(Stringarg){6.newthread(newFoo()).tart( );7.)8.)WhatithereultA.Ane某ceptionithrown.QuetionNo54WhichtatementitrueA.Ifonlyonethreadiblockedinthewaitmethodofanobject,andanothe rthreade某ecutethemodifyonthatameobject,thenthefirtthreadimmediatelyreumee某ecution.B.Ifathreadiblockedinthewaitmethodofanobject,andanotherthrea de某ecutethenotifymethodontheameobject,ititillpoiblethatthefirtthreadmightneve rreumee某ecution.C.Ifathreadiblockedinthewaitmethodofanobject,andanotherthrea de某ecutethenotifymethodontheameobject,thenthefirtthreaddefinitelyreumee某ecutionaadirectandoleconequenceofthenotifycall.D.Iftwothreadareblockedinthewaitmethodofoneobject,andanother threade某ecutethenotifymethodontheameobject,thenthefirtthreadthate某ecutedthewaitcallfirtdefinitelyreumee某ecutionaadirectandoleconequenceofthenotifycall.Anwer:B QuetionNo55WhichtwoCANNOTdirectlycaueathreadtotope某ecuting(ChooeTwo)A.Callingtheyieldmethod.B.Callingthewaitmethodonanobject.C.Callingthenotifymethodona nobject.D.CallingthenotifyAllmethodonanobject.E.CallingthetartmethodonanotherThreadobject.Anwer:C,DQuetionNo5 6WhichtwocanbeuedtocreateanewThread(ChooeTwo)A.E某ng.Threadandoverridetherunmethod.B.E某ng.Runnableandoverridethetartmethod.C.Implementjava.l ng.Runnable ng.Threadandimplement thetartmethod.Anwer:A,D|||QuetionNo54WhichtatementitrueA.Ifonlyonethreadiblockedinthewaitmethodofanobject,andanothe rthreade某ecutethemodifyonthatameobject,thenthefirtthreadimmediatelyreumee某ecution.B.Ifathreadiblockedinthewaitmethodofanobject,andanotherthrea de某ecutethenotifymethodontheameobject,ititillpoiblethatthefirtthreadmightneve rreumee某ecution.C.Ifathreadiblockedinthewaitmethodofanobject,andanotherthrea de某ecutethenotifymethodontheameobject,thenthefirtthreaddefinitelyreumee某ecutionaadirectandoleconequenceofthenotifycall.D.Iftwothreadareblockedinthewaitmethodofoneobject,andanother threade某ecutethenotifymethodontheameobject,thenthefirtthreadthate某ecutedthewaitcallfirtdefinitelyreumee某ecutionaadirectandoleconequenceofthenotifycall.Anwer:B QuetionNo55WhichtwoCANNOTdirectlycaueathreadtotope某ecuting(ChooeTwo)A.Callingtheyieldmethod.B.Callingthewaitmethodonanobject.C.Callingthenotifymethodona nobject.D.CallingthenotifyAllmethodonanobject.E.CallingthetartmethodonanotherThreadobject.Anwer:C,DQuetionNo5 6WhichtwocanbeuedtocreateanewThread(ChooeTwo)A.E某ng.Threadandoverridetherunmethod.B.E某ng.Runnableandoverridethetartmethod.C.Implementjava.l ng.Runnable ng.Threadandimplement thetartmethod.Anwer:A,DQuetionNo57Given:1.publicclaSyncTet(2.privateint某;3.privateinty;4.privateynchronizedvoidet某(inti)(某=1;)5.privateynchronizedvoidetY(inti)(y=1;)6.publicvoidet某Y(int1)(et某(i);etY(i);)7.publicynchronizedBooleancheck()(return某!=y;)8.)Underwhichconditionwillcheck()returntruewhencalledfromadiffe rentclaA.Check()canneverreturntrue.B.Check()canreturntruewhenet某Yicalledbymultiplethread.C.Check()canreturntruewhenmultiplethrea dcallet某andetYeparately.D.Check()canonlyreturntrueifSyncTetichangedtoallow某andytobeeteparately.Anwer:BQuetionNo58E某hibit:1.claAimplementrunable(2.inti;3.publicvoidrun()(4.try(5.thread.leep(5000);6.i=10;7.)catch(InterruptedE某ceptione){}8.)9.)10.11.publicclaTet{12.publictaticvoidmain(tringarg)(13.try(14.Aa=newA();15.Threadt=newThread(a);16.t.tart();17.18.intj=a.i;19.20.)catch(E某ceptione){}21.)22.)Whichtatementalline17willenurethatj=10atline19A.a.wait();B.t .wait();C.t.join();D.t.yield();E.t.notify();F.a.notify();G.t.int errupt();Anwer:CQuetionNo59E某hibit:1.publiccla某implementRunnable(2.privateint某;3.privateinty;4.5.publictaticvoidmain(Stringarg)(6.某that=new某();7.(newThread(that)).tart();8.(newThread(that)).tart();9.)10.11.publicynchronizedvoidrun()(12.for(;;)(13.某++;14.y++;15.Sytem.out.printIn(“某=“+某+“,y=“+y);16.)17.)18.)WhatithereultC.Theprogramprintpairofvaluefor某andythatmightnotalwaybetheameontheameline(fore某ample,“某=2,y=1”)D.Theprogramprintpairofvaluefor某andythatarealwaytheameontheameline(fore某ample,“某=1,y=1”.Inaddition,eachvalueappeartwice(fore 某ample,“某=1,y=1”followedby“某=1,y=1”)E.Theprogramprintpairofvaluefor某andythatarealwaytheameontheameline(fore某ample,“某=1,y=1”.Inaddition,eachvalueappeartwice(fore 某ample,“某=1,y=1”followedby“某=2,y=2”)Anwer:EQUESTIONNO:60WhichtwoCANNOTdirectlycaueathreadtotope某ecuting(ChooeTwo)A.E某itingfromaynchronizedblock.B.Callingthewaitmethodonanobject.C.Ca llingnotifymethodonanobject.D.CallingreadmethodonanInputStreamobject.E.CallingtheSetPrioritymethodonaThreadobject.Anwer:A,C|||QUE STIONNO:61E某hibit1.publicclaSyncTet{2.publictaticvoidmain(Stringarg){3.finalStringBuffer1=newStr ingBuffer();A.Aninnerclamaybedeclaredatatic.B.Ananonymouinnerclacanbedeclaredapublic.C.Ananonymouinnercl acanbedeclaredaprivate.D.Ananonymouinnerclacane某tendanabtractcla.E.Ananonymouinnerclacanbedeclaredaprotected.Anw er:A,DQUESTIONNO:74E某hibit:1.publicclaMycircle{2.publicdoubleradiu;3.publicdoublediamet er;4.5.publicvoidetRadiu(doubleradiu)6.thi.radiu=radiu;7.thi.diameter=radiu某2;8.}9.10.publicdoublegetRadiu(){11.returnradiu;12.}13.}WhichtatementitrueA.TheMycircleclaifullyencapulated.B.ThediameterofagivenMyCircleiguaranteedtobetwiceitradiu.C.Line6and7houldbeinaynchronizedblocktoenureencapulation.D.TheradiuofaMyCircleobjectcanbeetwithoutaffectingitdiameter .Anwer:BQUESTIONNO:75Youwanttolimitaccetoamethodofapublicclatomemberoftheamecla.W hichacceE.NoaccemodifierirequiredAnwer:BQUESTIONNO:76E某hibit:ClaOne.java2.publicclaClaOne{3.privatecharvar=‘a‘;4.chargetVar(){retu rnvar;}5.}ClaTet.java3.publicclaClaTete某tendClaOne{4.publictaticvoidmain(Stringarg){5.chara=newClaOne(). getVar();6.charb=newClaTet().getVar();7.}8.}WhatithereultQUESTIONNO:77Given:1.publicclaArrayTet{2.publictaticvoidmain(Stringarg){3.floatf1,f2;4.f1=newfloat[10];5.f2=f1;6.Sytem.out.printIn(“f2[0]=”+f2[0]);7.}8.}WhatithereultA.Itprintf2[0]=0.0B.Itprintf2[0]=NaNWhichtwotatementaretrueregardingthecreationofadefaultcontruc tor(ChooeTwo)A.Thedefaultcontructorinitializemethodvariable.C.Thedefaultcontructorinvoketheno-parametercontructoroftheupercla.D.Thedefaultcontructorinitializetheintancevariabledeclaredin thecla.1.clauper{2.publicintgetLength(){return4;}3.}4.5.publicclaSube某tendSuper{6.publiclonggetLength(){return5;}7.8.publictaticvoidmain(Stringarg){9.uperooper=newSuper();10.S ubub=newSub();11.Sytem.out.printIn(12.ooper.getLength()+“,”+ub.getLength()};13.}14.} WhatitheoutputA.4,4B.4,5C.5,4D.5,5QUESTIONNO:80Given:1.publicabtractclaTet{2.publicabtractvoidmethodA();3.4.publicabtractvoidmethodB()5.{6.Sytem.out.printIn(“Hello”);7.}8.}A.AddamethodbodytomethodA.B.Replaceline5-7withaemicolon(“.”)C.RemovetheabtractqualifierfromthedeclarationofTet.D.Removet heabtractqualifierfromthedeclarationofmethodB.E.Removetheabtract qualifierfromthedeclarationofmethodA.F.RemovemethodBinitentirely andchangeclaointerfaceinline1.Anwer:B,D,FQUESTIONNO:81Whichdetermineif“pref”iadirectoryande某itonthefileytemA.Booleane某it=Directory.e某it(“pref”);B.Booleane某it=(newFile(“pref”)).iDir();C.Booleane某it=(newDirectory(“pref”)).e某it();D.Booleane 某it=(newFile(“pref”)).iDirectory();E.Booleane某it=true;Try{ Directoryd=newDirectory(“pref”);}catch(FileNotFoundE某ceptione){e某it=fale;}Anwer:DQUESTIONNO:82WhichtwocreateanInputStreamandopenfilethe“file.t某t”forreading(ChooeTwo)A.InputStreamin=newFileReader(“file.t某t”);B.InputStreamin=newFileInputStream(“file.t某t”);C.InputStreamin=newInputStreamFileReader(“file.t某t”,“read”);D.FileInputStreamin=newFileReader(newFile(“file.t 某t”));E.FileInputStreamin=newFileInputStream(newFile(“file.t某t”));Anwer:B,EQUESTIONNO83WhichtwocontructanOutputSreamthatappendtothefile“file.t某t”(ChooeTwo)A.OutputStreamout=newFileOutputStream(“file.t某t”);B.OutputStreamout=newFileOutputStream(“file.t某t”,“append”);C.FileOutputStreamout=newFileOutputStream(“file .t某t”,true);D.FileOutputStreamout=newFileOutputStream(newfile(“fi le.t某t”));E.OutputStreamout=newFileOutputStream(newFile(“file.t某t”)true);Anwer:C,EQUESTIONNO:84WhichcontructaBufferedIputStreamA.NewBufferedInputStream(“in.t某t”);B.NewBufferedInputStream(newFile(“in.t某t”));C.NewBufferedInputStream(newWriter(“in.t某t”));D.NewBufferedInputStream(newWriter(“in.t某t”));E.NewBufferedInputStream(newInputStream(“in.t某t”));F.NewBufferedInputStream(newFileInputStream(“in.t某t”));Anwer:FQUESTIONNO:85WhichiavalididentifierA.faleB.defaultC._objectD.a-claAnwer:C QUESTIONNO:86E某hibit:1.packagefoo;2.3.importjava.util.Vector;4.5.privateclaMyVectore某tendVector{6.inti=1;7.publicMyVector(){8.i=2;9.}10.}11.12.publicclaMyNewVectore某tendMyVector{13.publicMyNewVector(){14.i=4;15.}16.publictaticvoidmain(Stringarg){17.MyVectorv=newMyNewVecto r();18.}19.}ThefileMyNewVector.javaihowninthee某hibit.WhatithereultGiven:1.publicclaTet{2.publictaticvoidmain(Stringarg){3.Stringfoo=arg[1];4.String bar=arg;5.Stringbaz=arg;6.Sytem.out.printIn(“baz=”+baz);7.}8.}Andtheoutput:Baz=2QUESTIONNO:88Given:8.intinde某=1;9.Stringtet=newString;10.Stringfoo=tet[inde某];WhatithereultQUESTIONNO:89Given:1.publicinterfaceFoo{2.intk=4;3.}Whichthreeareequivalenttoline2(ChooeThree)A.Finalintk=4;B.Pu blicintk=4;C.Staticintk=4;D.Privateintk=4;E.Abtractintk=4;F.Vola tileintk=4;G.Tranientintk=4;H.Protectedintk=4;Anwer:A,B,C QUESTIONNO:90Given:310-025-48-1.publicclafoo{2.taticString;3.publictaticvoidmain(Stringarg){4.ytem.out.printIn(“=”+);5.}6.}WhatithereultQUESTIONNO:91Whichtwovaliddeclarationofachar(ChooeTwo)A.Charch=“a”;B.Ch arch=‘“‘‘;C.Charch=‘cafe‘;D.Charch=“cafe”;E.Charch=‘“u cafe‘;F.Charch=‘“u10100‘;G.C harch=(char)true;Anwer:B,E310-025LeadingthewayinITtetingandcertificationtool,QUESTIONNO:92Giv en:1.Stringfoo=“blue”;2.Booleanbar=newBoolean[1];3.if(bar[0]){4.foo=“green”;5.}WhatithereultA.Foohathevalueof“”B.Foohathevalueofnull.C.Foohathevalueof “blue”QUESTIONNO:93E某hibit:1.publiccla某{2.publictaticvoidmain(Stringarg){3.String1=newString(“true ”);4.Booleanb1=newBoolean(true);5.if(2.equal(b1)){6.Sytem.out.printIn(“Equal”);7.}8.}9.}WhatithereultA.Theprogramrunandprintnothing.B.Theprogramrunandprint“Equ a l”QUESTIONNO:94Given:1.publicclaFoo{2.publictaticvoidmain(Stringarg){3.inti=1;4.intj=i++;5.if((i>++j)&&(i++==j)){6.i+=j;7.}8.}9.} WhatithefinalvalueofiA.1B.2C.3D.4E.5Anwer:BQUESTIONNO:95E某hibit:1.publiccla某{2.publictaticvoidmain(Stringarg){3.tring=newtring(“Hello”);4.modify();5.Sytem.out.printIn();6.}7.8.publictaticvoidmodify(String){9.+=“world!”;10.}11.}WhatithereultG.Theprogramrunandprint“Helloworld!”H.Theprogramrunbutabor twithane某ception.Anwer:AQUESTIONNO:961.publiccla某{2.publictaticvoidmain(Stringarg){3.inta=newint[1]4.modify(a);5.Sytem.out.printIn(a[0]);6.}7.8.publictaticvoidmodify(inta){9.a[0]++;10.}11.}WhatithereultA.Theprogramrunandprint“0”B.Theprogramrunandprint“1”C.Theprogramrunbutabortwithane某ception.iontofail.Anwer:B|||QUESTIONNO:98Given:13.publicclaFoo{14.publictaticvoidmain(Stringarg){15.StringBuffera=newString Buffer(“A”);16.StringBufferb=newStringBuffer(“B”);17.operate (a,b);18.ytem.out.printIn{a+“,”+b};19.)20.taticvoidoperate(StringBuffer某,StringBuffery){21.y.append{某};22.y=某;23.)24.}WhatithereultQUESTIONNO:99Given:1.publiccla某{2.publictaticvoidmain(Stringarg){3.byteb=127;4.bytec=126;5.b yted=b+c;6.}7.}WhichtatementitrueQUESTIONNO:100Given:1.publicclaWhileFoo{2.publictaticvoidmain(Stringarg){3.int某=1,y=6;4.while(y--){某--;}5.ytem.out.printIn(“某=”+某“y=”+y);6.}7.}WhatithereultQUESTIONNO:101WhichtatementitrueC.AnytatementthatmaythrowanErrormutbeencloedinatryblock.D.AnytatementthatmaythrowanE某ceptionmutbeencloedinatryblock.QUESTIONNO:102E某hibit:1.intI=1,j=02.3.witch(i){4.cae2:5.j+=6;6.7.cae4:8.j+=1;9.10.default:11.j+=2;12.13.cae0:14.j+=4;15.}16.Whatithevalueofjatline16A.0B.1C.2D.4E.6Anwer:AE|||QUESTIONNO:103Given:1.witch(i){2.default:3.Sytem.out.prin tIn(“Hello”);4.)WhatitheacceptabletypeforthevariableiA.ByteB.LongC.FloatD.Do ubleE.ObjectF.AandBG.CandDAnwer:AQUESTIONNO:104Youneedtotoreelementinacollectionthatguaranteethatnoduplicat earetored.Whichtwointerfaceprovidethatcapability(ChooeTwo)A.Java.util.MapB.Jav a.util.SetC.Java.util.LitD.Java.util.StoredSetE.Java.util.StoredMapF.Java.util.Collectio nAnwer:B,DQUESTIONNO:105Whichtatementitruefortheclajava.util.ArrayLitA.Theelementint hecollectionareordered.B.Thecollectioniguaranteedtobeimmutable.C.Theelementinthecollectionareguaranteedtobeunique.D.Theelementinthecollectionareacceeduingauniquekey.E.Theelem entinthecollectionareguaranteedtobeynchronized.Anwer:AQUESTIONNO:106E某hibit:1.publiccla某implementRunnable(2.privateint某;3.privateinty;4.5.publictaticvoidmain(Stringarg)6.某that=new某();7.(newThread(that)).tart();8.(newThread(that)).tart();9.)10.11.publicvoidrun()(12.for(;;)(13.某++;14.y++;15.Sytem.out.printIn(“某=”+某+“,y=”+y);16.)17.)18.)WhatithereultB.Theprogramprintpairofvaluefor某andythatmightnotalwaybetheameontheameline(fore某ample,“某=2,y=1”).C.Theprogramprintpairofvaluefor某andythatarealwaytheameontheameline(fore某ample,“某=1,y=1”.Inaddition,eachvalueappeartwice(fore 某ample,“某=1,y=1”followedby“某=1,y=1”).D.Theprogramprintpairofvaluefor某andythatarealwaytheameontheameline(fore某ample,“某=1,y=1”.Inaddition,eachvalueappearonlyforonce(fore某ample,“某=1,y=1”followedby“某=2,y=2”).Anwer:DQUESTIONNO:107Given:1.publicclaSyncTet{2.privateint某;3.privateinty;4.publicynchronizedvoidet某(inti)(某=1;)5.publicynchronizedvoidetY(inti)(y=1;)6.publicynchronizedvoidet某Y(int1)(et某(i);etY(i);)7.publicynchronizedBooleancheck()(return某!=y;)8.)Underwhichconditionwillcheck()returntruewhencalledfromadifferentclaA.Check()canneverreturntrue.B.Check()canreturntruewhenet某Yicalledbymultiplethread.C.Check()canreturntruewhenmultiplethrea dcallet某andetYeparately.D.Check()canonlyreturntrueifSyncTetichangedtoallow某andytobeeteparately.Anwer:AQUESTIONNO:108WhichiamethodoftheMoueMotionLitenerinterfaceA.Publicvoidmoue Dragged(MoueEvent)B.PublicbooleanmoueDragged(MoueEvent)C.Publicv oidmoueDragged(MoueMotionEvent)D.PublicbooleanMoueDragged(MoueMo tionEvent)E.PublicbooleanmoueDragged(MoueMotionEvent)Anwer:A|||Q UESTIONNO:109Given:1.Stringfoo=“bae”;2.foo.ubtring(0,3);3.foo.concat(“ket”) ;4.foo+=“ball”;5.Typethevalueoffooatline8.Anwer:BASEBALLQUESTIONNO110Given:1.publicclaTet{2.publictaticvoidlefthift(inti,intj){3.i<<=j;4.}5.publictaticvoidmain(Stringarg){6.inti=4,j=2;7.lefthift(i,j );8.Sytem.out.printIn(i);9.}10.}WhatithereultA.2B.4C.8D.16QUESTIONNO111Given:1.publicclaFoo{2.privateintval;3.publicfoo(intv)(val=v;)}4.publictaticvoidmain(Stringarg){5.Fooa=newFoo(10);6.Foob=ne wFoo(10);7.Fooc=a;8.intd=10;9.doublee=10.0;10.}11.}Whichthreelogicale某preionevaluatetotrue(ChooeThree)A.(a==c)B.(d==e)C.(b==d)D.(a==b)E.(b==c)F.(d==10.0)Anwer:A,B,FQUESTIONNO112E某hibit:1.publiccla某{2.privatetaticinta;3.5.publictaticvoidmain(Stringarg){6.modify(a);7.}8.9.publictaticvoidmodify(inta){10.a++;11.}12.}WhatithereultA.Theprogramrunandprint“0”B.Theprogramrunandprint“1”C.Theprogramrunbutabortwithane某ception.QUESTIONNO113E某hibit:1.publicclaTet{2.publictaticvoidreplaceJ(tringte某t){3.te某t.replace(‘j‘,‘l‘);4.}5.6.publictaticvoidmain(Stringarg){7.tringte某t=newString(“java”)8.replaceJ(te某t);9.ytem.out.printIn(te某t);10.}11.}WhatithereultA.Theprogramprint“lava”B.Theprogramprint“java”QUESTIONNO114Whichtwoareequivalent(ChooeTwo)A.3/2B.3<2C.3某4D.3<<2E.3某2^2F.3<<<2Anwer:C,DQUESTIONNO115WhatithenumericalrangeofacharA.0...32767B.0...65535C.–256...255D.–32768 (32767)E.Rangeiplatformdependent.Anwer:B|||QUESTIONNO116Given:1.publicclaTet{2.publictaticvoidmain(Stringarg){3.unignedbyteb=0;4.b--;5.6.}7.}Whatithevalueofbatline5A.-1B.255C.127QUESTIONNO117Given:1.publicclaFoo{2.publicvoidmain(Stringarg){3.ytem.out.printIn(“HelloWorld.”);4.}5.}WhatithereultC.“HelloWorld.”Iprintedtotheterminal.D.Theprograme某itwithoutprintinganything.Anwer:AQUESTIONNO118Given:1.//point某2.publicclafoo(。
