北京达内科技有限公司 Java培训讲师.doc

选择题 1:在软件生命周期中，下列哪个说法是不准确的? A.软件生命周期分为计划、开发和运行三个阶段 B.在计划阶段要进行问题焉醛和需求分析 C.在开发后期要进行编写代码和软件测试 D.在运行阶段主要是进行软件维护 2: 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; 3: Givethefollowingcode: publicclassExample publicstaticvoidmain(Stringargs) intl=0; do System.out.println(“Doingitforlis:”+l); while(-l0) System.out.println(“Finish”); Whichwellbeoutput:Give the following code:public class Examplepublic static void main(String args )int l=0;doSystem.out.println(“Doing it for l is:”+l);while(-l0)System.out.println(“Finish”);Which well be output: A.Doing it for l is 3 B.Doing it for l is 1 C.Doing it for l is 2 D.Doing it for l is 0 4: 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 5: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. 6: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 7:What is written to the standard output given the following statement:System.out.println(4|7); Select the right answer: A.4 B.5 C.6 D.7 8: 1.publicclassX 2.publicobjectm() 3.objecto=newfloat(3.14F); 4.objectoa=newobject1; 5.oa0=o; 6.o=null; 7.oa0=null; 8.returno; 9. 10. Whenisthefloatobjectcreatedinline3,eligibleforgarbagecollection? 1. public class X 2. public object m () 3. object o = new float (3.14F); 4. object oa = new object 1; 5. oa0= o; 6. o = null; 7. oa0 = null; 8.return o; 9. 10. 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 D.Just after line 8(that is, as the method returns) 9: Consider the class hierarchy shown below: - class FourWheeler implements DrivingUtilities class Car extends FourWheeler class Truck extends FourWheeler class Bus extends FourWheeler class Crane extends FourWheeler - Consider the following code below: 1.DrivingUtilities du; 2.FourWheeler fw; 3.Truck myTruck = new Truck(); 4.du = (DrivingUtilities)myTruck; 5.fw = new Crane(); 6.fw = du; Which of the statements below are true? Choices: A.Line 4 will not compile because an interface cannot refer to an object. B.The code will compile and run. C.The code will not compile without an explicit cast at line 6, because going down the hierarchy without casting is not allowed. D.The code will compile if we put an explicit cast at line 6 but will throw an exception at runtime. 10: Givethefollowingmethod: publicvoidmethod() Stringa,b; a=newString(“helloworld”); b=newString(“gameover”); System.out.println(a+b+”ok”); a=null; a=b; System.out.println(a); Intheabsenceofcompileroptimization,whichistheearliestpointtheobjectareferedisdefinitelyelibiletobegarbagecollection.Give the following method: public void method( ) String a,b; a=new String(“hello world”); b=new String(“game over”); System.out.println(a+b+”ok”); a=null; a=b; System.out.println(a); In the absence of compiler optimization, which is the earliest point the object a refered is definitely elibile to be garbage collection.A.before line 5 B.before line 6 C.before line 7 D.before line 9 11: Whatwillhappenwhenyouattempttocompileandrunthefollowingcode? publicclassStatic static intx=5; staticintx,y; publicstaticvoidmain(Stringargs) x-; myMethod(); System.out.println(x+y+x); publicstaticvoidmyMethod() y=x+x; Choices:What will happen when you attempt to compile and run the following code? public class Staticstaticint x = 5; static int x,y;public static void main(String args) x-; myMethod(); System.out.println(x + y + +x); public static void myMethod()y = x+ + +x; Choices:A.prints : 2 B.prints : 3 C.prints : 7 D.prints : 8 12: Whatwillbetheresultofexecutingthefollowingcode? publicstaticvoidmain(Stringargs) chardigit=a; for(inti=0;i10;i+) switch(digit) casex: intj=0; System.out.println(j); default: intj=100; System.out.println(j); inti=j; System.out.println(i); Choices:What will be the result of executing the following code? public static void main(String args) char digit = a; for (int i = 0; i 10; i+) switch (digit) case x : int j = 0; System.out.println(j); default : int j = 100;System.out.println(j); int i = j; System.out.println(i); Choices:A.100 will be printed 11 times. B.The code will not compile because the variable i cannot be declared twice within the main() method. C.The code will not compile because the variable j cannot be declared twice within the switch statement. D.None of these. 13:软件生命周期的瀑布模型把软件项目分为3个阶段、8个子阶段，以下哪一个是正常的开发顺序? A.计划阶段、开发阶段、运行阶段 B.设计阶段、开发阶段、编码阶段 C.设计阶段、编码阶段、维护阶段 D.计划阶段、编码阶段、测试阶段 14:设有变量说明语句int a=1,b=0; 则执行以下程序段的输出结果为（ ）。 switch (a) case 1: switch (b) case 0:printf(*0*);break; case 1:printf(*1*);break; case 2:printf(*2*);break; printf(n); A.*0* B.*0*2* C.*0*1*2* D.有语法错误 15: Whatwillhappenwhenyouattempttocompileandrunthefollowingcode? classBase inti=99; publicvoidamethod() System.out.println(Base.amethod(); Base() amethod(); publicclassDerivedextendsBase inti=-1; publicstaticvoidmain(Stringargv) Baseb=newDerived(); System.out.println(b.i); b.amethod(); publicvoidamethod() System.out.println(Derived.amethod(); Choices:What will happen when you attempt to compile and run the following code? class Base int i = 99; public void amethod() System.out.println(Base.amethod(); Base() amethod(); public class Derived extends Baseint i = -1; public static void main(String a