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选择题 1: Whatwillbetheresultofexecutingthefollowingcode? /Filename;SuperclassX.java packagepackageX; publicclassSuperclassX protectedvoidsuperclassMethodX() intsuperclassVarX; /FilenameSubclassY.java 1.packagepackageX.packageY; 2. 3.publicclassSubclassYextendsSuperclassX 4. 5.SuperclassXobjX=newSubclassY(); 6.SubclassYobjY=newSubclassY(); 7.voidsubclassMethodY() 8. 9.objY.superclassMethodX(); 10.inti; 11.i=objY.superclassVarX; 12. 13. Choices:What will be the result of executing the following code? / Filename; SuperclassX.javapackage packageX; public class SuperclassXprotected void superclassMethodX()int superclassVarX; / Filename SubclassY.java1.package packageX.packageY;2.3.public class SubclassY extends SuperclassX4.5.SuperclassX objX = new SubclassY();6.SubclassY objY = new SubclassY();7.void subclassMethodY()8.9.objY.superclassMethodX();10.int i;11.i = objY.superclassVarX;12.13. Choices:A.Compilation error at line 5 B.Compilation error at line 9 C.Runtime exception at line 11 D.None of these 2: ThefollowingcodeisentirecontentsofafilecalledExample.java,causespreciselyoneerrorduringcompilation: classSubClassextendsBaseClass classBaseClass() Stringstr; publicBaseClass() System.out.println(“ok”); publicBaseClass(Strings) str=s; publicclassExample publicvoidmethod() SubClasss=newSubClass(“hello”); BaseClassb=newBaseClass(“world”); Whichlinewouldbecausetheerror?The following code is entire contents of a file called Example.java,causes precisely one error during compilation: class SubClass extends BaseClass class BaseClass() String str; public BaseClass() System.out.println(“ok”); public BaseClass(String s) str=s; public class Example public void method() SubClass s=new SubClass(“hello”); BaseClass b=new BaseClass(“world”); Which line would be cause the error? A.9 B.10 C.11 D.12 3:鉴于Java的特点，它最适合的计算环境是 A.并行计算环境 B.分布式计算环境 C.高强度计算环境 D.开放式计算环境 4: Whatwillbeprintedwhenyouexecutethefollowingcode? classX Yb=newY(); X() System.out.print(X); classY Y() System.out.print(Y); publicclassZextendsX Yy=newY(); Z() System.out.print(Z); publicstaticvoidmain(Stringargs) newZ(); Choices:What will be printed when you execute the following code? class X Y b = new Y(); X() System.out.print(X); class Y Y() System.out.print(Y); public class Z extends X Y y = new Y(); Z() System.out.print(Z); public static void main(String args) new Z(); Choices:A.Z B.YZ C.XYZ D.YXYZ 5: Giventhefollowingclassdefinition: classA protectedinti; A(inti) this.i=i; whichofthefollowingwouldbeavalidinnerclassforthisclass? Selectvalidanswer:Given the following class definition:class Aprotected int i;A(int i)this.i=i;which of the following would be a valid inner class for this class?Select valid answer: A.class B B.class B extends A C.class B extends A B()System.out.println(“i=”+i); D.class B class A 6: 下述程序代码中有语法错误的行是（）。 inti,ia10,ib10;/*第一行*/for(i=0;i=9;i+)/*第2行*/iai=0;/*第3行*/ib=ia;/*第4行*/下述程序代码中有语法错误的行是（ ）。int i,ia10,ib10; /*第一行*/for (i=0;i=9;i+) /*第2行*/ iai=0; /*第3行*/ib=ia; /*第4行*/A.第1行 B.第2行 C.第3行 D.第4行 7: Givethisclassoutline: classExample privateintx; /restofclassbody AssumingthatxinvokedbythecodejavaExample,whichstatementcanmadexbedirectlyaccessibleinmain()methodofExample.java?Give this class outline:class Exampleprivate int x;/rest of class bodyAssuming that x invoked by the code java Example, which statement can made x be directly accessible in main() method of Example.java?A.Change private int x to public int x B.change private int x to static int x C.Change private int x to protected int x D.change private int x to final int x 8:假定a和b为int型变量,则执行下述语句组后,b的值为 a=1; b=10; do b-=a; a+; while (b-0); A.9 B.-2 C.-1 D.8 9: publicclassOuterClass privatedoubled1=1.0; /insertcodehere Youneedtoinsertaninnerclassdeclarationatline3.Whichtwoinnerclassdeclarationsare valid?public class OuterClass private double d1 = 1.0;/insert code hereYou need to insert an inner class declaration at line 3. Which two inner class declarations arevalid?A.class InnerOne public static double methoda() return d1; B.public class InnerOne static double methoda() return d1; C.private class InnerOne double methoda() return d1; D.static class InnerOne protected double methoda() return d1; 10:Which are not Java keywords? A.TRUE B.const C.super D.void 11:In the following pieces of code, which one will compile without any error? A.StringBuffer sb1 = abcd; B.Boolean b = new Boolean(abcd); C.C: byte b = 255; D.float fl = 1.2; 12: publicclassX publicObjectm() Objecto=newFloat(3.14F);/line3 Objectoa=newObject1;/line4 oa0=o;/line5 o=null;/line6 returnoa0;/line7 WhenistheFloatobject,createdinline3,eligibleforgarbagecollection?public class X public Object m() Object o = new Float(3.14F);/line 3 Object oa = new Object1;/line 4 oa0 = o;/line 5 o=null;/line 6 return oa0;/line 7 When is the Float object, created in line 3,eligible for garbage collection?A.just after line 5. B.just after line 6 C.just after line 7(that is,as the method returns) D.never in this method 13: Givethefollowingjavasourcefragement: /pointx publicclassInteresting /dosomething WhichstatementiscorrectlyJavasyntaxatpointx?Give the following java source fragement:/point xpublic class Interesting/do somethingWhich statement is correctly Java syntax at point x? A.public class MyClass/do other thing B.static int PI=3.14 C.class MyClass/do something D.none 14:Which of the following statements are not legal? A.long l = 4990; B.int i = 4L; C.double d = 34.4; D.double t = 0.9F. 15: Whatwillhappenwhenyouattempttocompileandrunthefollowingcode? intOutput=10; booleanb1=false; if(b1=true)&(Output+=10)=20) System.out.println(Weareequal+Output); else System.out.println(Notequal!+Output); Choices:What will happen when you attempt to compile and run the following code? int Output = 10;boolean b1 = false; if(b1 = true) & (Output += 10) = 20) System.out.println(We are equal + Output); else System.out.println(Not equal! + Output); Choices:A.Compilation error, attempting to perform binary comparison on logical data type B.Compilation and output of We are equal 10. C.Compilation and output of Not equal! 20. D.Compilation and output of Not equal! 10. 16: Whatwillbetheresultofexecutingthefollowingcode? booleana=true; booleanb=false; booleanc=true; if(a=true) if(b=true) if(c=true)System.out.println(Somethingsaretrueinthisworld); elseSystem.out.println(Nothingistrueinthisworld!); elseif(a&(b=c)System.out.println(Itstooconfusingtotellwhatistrueandwhatisfalse); elseSystem.out.println(Heythiswontcompile); Choices:What will be the result of executing the following code? boolean a = true; boolean b = false; boolean c = true; if (a = true) if (b = true) if (c = true) System.out.println(Some things are true in this world); else System.out.println(Nothing is true in this world!); else if (a & (b = c) System.out.println(Its too confusing to tell what is true and what is false); else System.out.println(Hey this wont compile); Choices:A.The code wont compile B.Some things are true in this world will be printed C.Hey this wont compile will be printed D.None of these 17: 给出下面的代码片断。下面的哪些陈述为错误的? 1)publicvoidcreate() 2)VectormyVect; 3)myVect=newVector(); 4)给出下面的代码片断。下面的哪些陈述为错误的?1) public void create() 2) Vector myVect;3) myVect = new Vector();4) A.第二行的声明不会为变量myVect分配内存空间。 B.第二行语句创建一个Vector类对象。 C.第三行语句创建一个Vector类对象。 D.第三行语句为一个Vector类对象分配内存空间 18:Which statement about listener is true? A.Most component allow multiple listeners to be added. B.If multiple listener be add to a single component, the event only affected one listener. C.Component don?t allow multiple listeners to be add. D.none 19: SelectvalididentifierofJava:Select valid identifier of Java:A.%passwd B.3d_game C.$charge D.this 20: Whichisthemostappropriatecodesnippetthatcanbeinsertedatline18inthefollowingcode? (Assumethatthecodeiscompiledandrunwithassertionsenabled) 1.importjava.util.*; 2. 3.publicclassAssertTest 4. 5.privateHashMapcctld; 6. 7.publicAssertTest() 8. 9.cctld=newHashMap(); 10.cctld.put(in,India); 11.cctld.put(uk,UnitedKingdom); 12.cctld.put(au,Australia); 13./morecode. 14. 15./othermethods. 16.publicStringgetCountry(StringcountryCode) 17. 18./Whatshouldbeinsertedhere? 19.Stringcountry=(String)cctld.get(countryCode); 20.returncountry; 21. 22.Which is the most appropriate code snippet that can be inserted at line 18 in the following code?(Assume that the code is compiled and run with assertions enabled)1. import java.util.*;2. 3. public class AssertTest4. 5. private HashMap cctld;6. 7. public AssertTest()8. 9. cctld = new HashMap();10. cctld.put(in, India);11. cctld.put(uk, United Kingdom);12. cctld.put(au, Australia);13. / more code. 14. 15. / other methods . 16. public String getCountry(String countryCode)17. 18. / What should be inserted here?19. String country = (String)cctld.get(countryCode);20. return country;21. 22. A.assert countryCode != null; B.assert countryCode != null : Country code can not be null ; C.assert cctld != null : No country code data is available; D.assert cctld : No country code data is available; 21: Whatistheresultwhenyoucompileandrunthefollowingcode? publicclassTest publicvoidmethod() for(inti=0;i3;i+) System.out.print(i); System.out.print(i); Choices:What is the result when you compile and run the following code? public class Test public void method()for(int i = 0; i 3; i+) System.out.print(i); Sys