8:00 Quiz 5

Statistics:

(including 5-point curve)

mean     22.317 (915.000/41)
stddev   5.425
median   22.000
midrange 19.000-25.000

# avg
1 6.66 / 10
2 4.83 / 10
3 5.83 / 10
 + 5-point curve

Question 5-1

Select which of the following best describes the purpose of each of the circled pieces of the code. (Note that some choices may not appear at all, and others may occur multiple times.)

A. local variable declaration
B. class variable declaration
C. instance variable declaration
D. constructor method definition
E. class method definition
F. instance method definition

Solution

Question 5-2

Complete the method body so that it removes all strings in list beginning with the letter initial. It should assume that list contains only String objects.

public static void removeAll(ArrayList list, char initial) {



}

Recall the following instance methods defined for the ArrayList class.

Object get(int index): Returns the object at index index of the list.
Object remove(int index): Removes the object at index index of the list, shifting objects at that index and beyond to fill the gap. Returns the removed object.
int size(): Returns the number of elements in the list.

Also recall the following instance method defined for the String class.

char charAt(int pos): Returns the character at index pos of the string.

Solution

Question 5-3

Define a class NumberIterator for iterating through a sequence of numbers. It should support the following methods.

NumberIterator(int start, int stop): (Constructor method) Constructs an object for iterating through the integers beginning at start and going up to stop. The constructor assumes that start is less than stop.
boolean hasMoreNumbers(): Returns true if there are more numbers remaining in the sequence.
int nextNumber(): Returns the current number in the sequence and steps the iterator forward, so that the next call to this method returns the following number in the sequence. This method initiates a NoSuchElementException if the sequence has no more elements remaining.

For example, if you defined this class properly, I should be able to write the following class to test it. When executed, its run() method would print ``5 6 7 8''.

public class NumberIteratorTest {
    public static void run() {
        NumberIterator it = new NumberIterator(5, 8);
        IO.print(it.nextNumber());
        while(it.hasMoreNumbers()) {
            int i = it.nextNumber();
            IO.print(" " + i);
        }
    }
}

Solution