java程序员认证考试试题

1、java程序员认证考试试题1.Which statement about the garbage collection mechanism are true?A. Garbage collection require additional programe code in cases where multiple threads are running.B. The programmer can indicate that a reference through a local variable is no longer of interest.C. The programmer has a

2、mechanism that explicity and immediately frees the memory used by Java objects.D. The garbage collection mechanism can free the memory used by Java Object at explection time.E. The garbage collection system never reclaims memory from objects while are still accessible to running user threads.2. Give

3、 the following method:1) public void method( )2) String a,b;3) a=new String(“hello world”);4) b=new String(“game over”);5) System.out.println(a+b+”ok”);6) a=null;7) a=b;8) System.out.println(a);9) In the absence of compiler optimization, which is the earliest point the object a refered is definitely

4、 elibile to be garbage collection.A. before line 3B.before line 5C. before line 6D.before line 7E. Before line 93. In the class java.awt.AWTEvent,which is the parent class upon which jdk1.1 awt events are based there is a method called getID which phrase accurately describes the return value of this

5、 method?A. It is a reference to the object directly affected by the cause of the event.B. It is an indication of the nature of the cause of the event.C. It is an indication of the position of the mouse when it caused the event.D. In the case of a mouse click, it is an indication of the text under th

6、e mouse at the time of the event.E. It tells the state of certain keys on the keybord at the time of the event.F. It is an indication of the time at which the event occurred.4. Which statement about listener is true?A. Most component allow multiple listeners to be added.B. If multiple listener be ad

7、d to a single component, the event only affected one listener.C. Component don?t allow multiple listeners to be add.D. The listener mechanism allows you to call an addXxxxListener method as many times as is needed, specifying as many different listeners as your design require.5.Give the following co

8、de:public class Examplepublic static void main(String args )int l=0;doSystem.out.println(“Doing it for l is:”+l);while(-l>0)System.out.println(“Finish”);Which well be output:A. Doing it for l is 3B. Doing it for l is 1C. Doing it for l is 2D. Doing it for l is 0E. Doing it for l is ?C1F. Finish6.

9、 Give the code fragment:1) switch(x)2) case 1:System.out.println(“Test 1”);break;3) case 2:4) case 3:System.out.println(“Test 2”);break;5) default:System.out.println(“end”);6) which value of x would cause “Test 2” to the output:A. 1B. 2C. 3D. default7. Give incompleted method:1)2) if(unsafe()/do som

10、ething3) else if(safe()/do the other4) The method unsafe() well throe an IOException, which completes the method of declaration when added at line one?A. public IOException methodName()B. public void methodName()C. public void methodName() throw IOExceptionD. public void methodName() throws IOExcept

11、ionE. public void methodName() throws Exception8. Give the code fragment:if(x>4)System.out.println(“Test 1”);else if (x>9)System.out.println(“Test 2”);else System.out.println(“Test 3”);Which range of value x would produce of output “Test 2”?A. x<4B. x>4C. x>9D. None9. Give the followi

12、ng method:public void example()tryunsafe();System.out.println(“Test1”);catch(SafeException e)System.out.println(“Test 2”);finallySystem.out.println(“Test 3”);System.out.println(“Test 4”);Which will display if method unsafe () run normally?A. Test 1B. Test 2C. Test 3D. Test 410. Which method you defi

13、ne as the starting point of new thread in a class from which new the thread can be excution?A. public void start()B. public void run()C. public void int()D. public static void main(String args)E. public void runnable()11.Given the following class definition:class Aprotected int i;A(int i)this.i=i;wh

14、ich of the following would be a valid inner class for this class?Select all valid answers:A. class BB. class B extends AC. class B extends AB()System.out.println(“i=”+i);D. class Bclass AE. class A12. Which modifier should be applied to a method for the lock of object this to be obtained prior to ex

15、cution any of the method body?A. synchronizedB. abstractC. finalD. staticE. public13. The following code is entire contents of a file called Example.java,causes precisely one error during compilation:1) class SubClass extends BaseClass2) 3) class BaseClass()4) String str;5) public BaseClass()6) Syst

16、em.out.println(“ok”);7) public BaseClass(String s)8) str=s;9) public class Example10) public void method()11) SubClass s=new SubClass(“hello”);12) BaseClass b=new BaseClass(“world”);13) 14) Which line would be cause the error?A. 9 B. 10 C. 11 D.1214. Which statement is correctly declare a variable a

17、 which is suitable for refering to an array of 50 string empty object?A. String aB. String aC. char aD. String a50F. Object a5015. Give the following java source fragement:/point xpublic class Interesting/do somethingWhich statement is correctly Java syntax at point x?A. import java.awt.*;B.package

18、mypackageC. static int PI=3.14D. public class MyClass/do other thing E. class MyClass/do something16. 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.

19、java?A. Change private int x to public int xB. change private int x to static int xC. Change private int x to protected int xD. change private int x to final int x17. the piece of preliminary analsis work describes a class that will be used frequently in many unrelated parts of a project“The polygon

20、 object is a drawable, A polygon has vertex information stored in a vector, a color, length and width.”Which Data type would be used?A. VectorB. intC. StringD. ColorE. Date18. A class design requires that a member variable should be accessible only by same package, which modifer word should be used?

21、A. protectedB. publicC. no modiferD. private19.Which declares for native method in a java class corrected?A. public native void method()B. public native void method();C. public native method();D. public void method()native;E. public void native method();20. Which modifer should be applied to a decla

22、ration of a class member variable for the value of variable to remain constant after the creation of the object?21. Which is the main() method return of a application?A. StringB. byteC. charD. void22. Which is corrected argument of main() method of application?A. String argsB. String arC. Char argsD. StringBuffer arg23. “The Employee object is a person, An Employee has appointment store in a vector, a hire date and a number of dependent”short answer: use shortest statement declare a class of Employee.24. Give the following class defination inseparate source fil