Java开发工程师 笔试题.docx

1、Java开发工程师 笔试题选择题 1: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. 2: Whatwillhappenwhenyouattempttocompileandrunthefollowingcode? publicclassStatic static intx=5; staticintx,y; publicstaticvoidmain(Stringargs) x-; myMethod(); Sys

2、tem.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 myMeth

3、od()y = x+ + +x; Choices:A.prints : 2 B.prints : 3 C.prints : 7 D.prints : 8 3: Givethecodefragment: if(x4) System.out.println(“Test1”); elseif(x9) System.out.println(“Test2”); else System.out.println(“Test3”); Whichrangeofvaluexwouldproduceofoutput“Test2”?Give the code fragment:if(x4)System.out.pri

4、ntln(“Test 1”);else if (x9)System.out.println(“Test 2”);else System.out.println(“Test 3”);Which range of value x would produce of output “Test 2”? A.x4 C.x9 D.None 4:Math.round(-11.5)等於多少? A.-11 B.-12 C.-11.5 D.none 5:public class Parent int change() class Child extends Parent Which methods can be a

5、dded into class Child? A.public int change() B.abstract int chang() C.private int change() D.none 6: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 7: Givethefollowingjavaclass: publicclassExample publicstaticvoidmain(Stringargs) staticintx=newin

6、t15; System.out.println(x5); Whichstatementiscorrected?Give the following java class:public class Examplepublic static void main(String args)static int x = new int15;System.out.println(x5);Which statement is corrected?A.When compile, some error will occur. B.When run, some error will occur. C.Output

7、 is zero. D.Output is null. 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: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 10: Whatwillhappenwhenyouattempttocompileandrunthefollowingcode? classBas

8、e 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 whe

9、n 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 argv) Base b = new Derived(); System.out.println(b.i); b.amethod(); publi

10、c void amethod() System.out.println(Derived.amethod(); Choices:A.Derived.amethod() -1 Derived.amethod() B.Derived.amethod() 99 C.Compile time error D.Derived.amethod() 11: Givethisclassoutline: classExample privateintx; /restofclassbody AssumingthatxinvokedbythecodejavaExample,whichstatementcanmadex

11、bedirectlyaccessibleinmain()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

12、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 12: Whichisthemostappropriatecodesnippetthatcanbeinsertedatline18inthefollowingcode? (Assumethatthecodeiscompiledandrunwithassertionsenabled) 1.importjava.util.*; 2. 3.publicclassAssertTest

13、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)c

14、ctld.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. publ

15、ic 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(

16、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; 13: 给出下面的代码片断。下面的哪些陈述为错误的? 1)publicvoidcreate() 2)Vector

17、myVect; 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 14: Givethefollowingjavasourcefragement: /pointx publicclassInteresting /dosomet

18、hing 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 15:Which statemen

19、t 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 16: publicclassX publicObjectm() Objecto=newFloat(3.14F);/line3 Obj

20、ectoa=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 Floa

21、t 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 17: Whatwillbeprintedwhenyouexecutethefollowingcode? classX Yb=newY(); X() System.out.print(X); classY Y() System.out.print(Y

22、); 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.o

23、ut.print(Z); public static void main(String args) new Z(); Choices:A.Z B.YZ C.XYZ D.YXYZ 简答题 18:swtich是否能作用在byte上，是否能作用在long上，是否能作用在String上? 19:Static Inner Class 和 Inner Class的不同，说得越多越好。 20:请说出你所知道的线程同步的方法。 21:一堆数在一个集合中，总共2n个，问如何将这些数分成A，B两分，每分n个，要求A中的数均小于B中的数，需要考虑时间复杂度。 22: packagetest; publicclass

24、FatherClass publicFatherClass() System.out.println(FatherClassCreate); 子类: packagetest; importtest.FatherClass; publicclassChildClassextendsFatherClass publicChildClass() System.out.println(ChildClassCreate); publicstaticvoidmain(Stringargs) FatherClassfc=newFatherClass(); ChildClasscc=newChildClass(); 输出结果：package test;public class FatherClasspublic FatherClass()Sy