JAVA题库:格林模拟试题二（上）6

　　Question 17)
　　Which statements are correct about the anchor field?
　　1) It is a field of the GridBagLayout manager for controlling component placement
　　2) It is a field of the GridBagConstraints class for controlling component placement
　　3) A valid setting for the anchor field is GridBagConstraints.NORTH
　　4) The anchor field controls the height of components added to a container
　　Question 18)
　　What will happen when you attempt to compile and run the following code?
　　public class Bground extends Thread{public static void main(String argv[]){                Bground b = new Bground();                b.run();        }        public void start(){                for (int i = 0; i <10; i++){                        System.out.println("Value of i = " + i);                }        }}
　　1) A compile time error indicating that no run method is defined for the Thread class
　　2) A run time error indicating that no run method is defined for the Thread class
　　3) Clean compile and at run time the values 0 to 9 are printed out
　　4) Clean compile but no output at runtime
　　Question 19)
　　Is the following statement true or false?
　　When using the GridBagLayout manager, each new component requires a new instance of the GridBagConstraints class.
　　1) true
　　2) false
　　Question 20)
　　Which most closely matches a description of a Java Map?
　　1) A vector of arrays for a 2D geographic representation
　　2) A class for containing unique array elements
　　3) A class for containing unique vector elements
　　4) An interface that ensures that implementing classes cannot contain duplicate keys
　　Question 21)
　　How does the set collection deal with duplicate elements?
　　1) An exception is thrown if you attempt to add an element with a duplicate value
　　2) The add method returns false if you attempt to add an element with a duplicate value
　　3) A set may contain elements that return duplicate values from a call to the equals method
　　4) Duplicate values will cause an error at compile time