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）