test of the java skill（3）_java认证

Question 17:
　　 What will happen when you attempt to compile and run this code?
　　 class Base{
　　 abstract public void myfunc();
　　 public void another(){
　　 System.out.println(“Another method”);
　　 }
　　 }

　　 public class Abs extends Base{
　　 public static void main(String argv[]){
　　 Abs a = new Abs();
　　 a.amethod();
　　 }
　　 public void myfunc(){
　　 System.out.println(“My func”);
　　 }
　　 public void amethod(){
　　 myfunc();
　　 }
　　 }

　　 A. The code will compile and run, printing out the words “My func”

　　 B. The compiler will complain that the Base class is not declared as abstract.

　　 C. The code will compile but complain at run time that the Base class has non abstract methods

　　 D. The compiler will complain that the method myfunc in the base class has no body

　　 Question 18:
　　 You need to create a class that will store some unique object elements. You do not need to sort these elements but they must be unique.

　　 What interface might be most suitable to meet this need?

　　 A. Set

　　 B. List

　　 C. Map

　　 D. Vector

　　 Question 19:
　　 What will happen when you attempt to compile and run the following code?

　　 class Background implements Runnable{
　　 int i = 0;
　　 public int run(){
　　 while(true){
　　 i++;
　　 System.out.println(“i=” + i);
　　 }//End while
　　 }//End run
　　 }//End class

　　 A. It will compile and the run method will print out the increasing value of i

　　 B. It will compile and calling start will print out the increasing value of i

　　 C. The code will cause an error at compile time

　　 D. Compilation will cause an error because while cannot take a parameter of true

　　 Question 20:
　　 Given the following code how could you invoke the Base constructor that will print out the string “base constructor”?
　　 class Base{
　　 Base (int i){
　　 System.out.println(“base constructor”);
　　 }
　　 Base(){
　　 }
　　 }

　　 public class Sup extends Base{
　　 public static void main(String argv[]){
　　 Sup s = new Sup();
　　 // One
　　 }
　　 Sup(){
　　 // Tow
　　 }
　　 public void derived(){
　　 // Three
　　 }
　　 }

　　 A. On the line After // One put Base(10);

　　 B. On the line After // One put super(10);

　　 C. On the line After // Two put super(10);

　　 D. On the line After // Three put super(10);

　　 Question 21:
　　 Why might you define a method as native?
　　 A. To get to access hardware that Java does not know about

　　 B. To define a new data type such as an unsigned integer

　　 C. To write optimized code for performance in a language such as C/C++

　　 D. To overcome the limitation of the private scope of a method

　　 Question 22:
　　 What will happen when you attempt to compile and run the following code with the command line “hello there”?

　　 public class Arg{
　　 String[] MyArg;
　　 public static void main(String argv[]){
　　 MyArg = argv;
　　 }
　　 public void amethod(){
　　 System.out.println(argv[1]);
　　 }
　　 }

　　 A. Compile time error

　　 B. Compilation and output of “hello”

　　 C. Compilation and output of “there”

　　 D. None of the above

　　 Question 23:
　　 What will be printed out if this code is run with the following command line?
　　 java myprog good morning

　　 public class myporg{　
　　 public static void main(String argv[]){
　　 System.out.println(argv[2]);
　　 }
　　 }

　　 A. myprog

　　 B. good

　　 C. morning

　　 D. Exception raised: “java.lang.ArrayIndexOutOfBoundsException: 2”

　　 Question 24:
　　 What will happen when you attempt to compile and run the following code?

　　 public class Hope{
　　 public static void main(String argv[]){
　　 Hope h = new Hope();
　　 }

　　 protected Hope(){
　　 for (int i=0; i<10; i++){
　　 System.out.println(i);
　　 }
　　 }
　　 }

　　 A. Compilation error: Constructors cannot be declared protected

　　 B. Run time error: Constructors cannot be declared protected

　　 C. Compilation and running with output 0 to 10

　　 D. Compilation and running with output 0 to 9（CN-JAVA）