1. Information and Computer Sciences University of Hawaii, Manoa
Midterm 1 Solutions
ICS 211
Cam Moore
Information and Computer Sciences
University of Hawaii, Manoa

2. 2 3 Question 1 String x = new String(“cat”);
String y = new String(“cat”);
String z = x;
How many objects are created?
How many references?
Is x == y true or false
Is x.equals(y) true or false 2 3

3. Question 2 Write the List<E> interface:
/** An ordered collection. The user can access elements by their
* integer index, and search for elements in the list. */
public interface List<E> extends Collection<E> {
E get(int index); // returns object at given position
E set(int index, E element); // sets element, returns old value
E remove(int index); // removes object at the given position
int size(); // returns number of elements in list
boolean add(E element); // add element at the end of the list
void add(int index, E element); // add element at given position
int indexOf(Object o); // returns index of object in list
... }

4. Question 2 Write the List<E> interface:
/** An ordered collection. The user can access elements by their
* integer index, and search for elements in the list. */
public interface List<E> extends Collection<E> {
E get(int index); // returns object at given position
E set(int index, E element); // sets element, returns old value
E remove(int index); // removes object at the given position
int size(); // returns number of elements in list
boolean add(E element); // add element at the end of the list
void add(int index, E element); // add element at given position
int indexOf(Object o); // returns index of object in list
... }

5. Question 2 Write the List<E> interface:
/** An ordered collection. The user can access elements by their
* integer index, and search for elements in the list. */
public interface List<E> extends Collection<E> {
E get(int index); // returns object at given position
E set(int index, E element); // sets element, returns old value
E remove(int index); // removes object at the given position
int size(); // returns number of elements in list
boolean add(E element); // add element at the end of the list
void add(int index, E element); // add element at given position
int indexOf(Object o); // returns index of object in list
... }

6. Question 2 Write the List<E> interface:
/** An ordered collection. The user can access elements by their
* integer index, and search for elements in the list. */
public interface List<E> extends Collection<E> {
E get(int index); // returns object at given position
E set(int index, E element); // sets element, returns old value
E remove(int index); // removes object at the given position
int size(); // returns number of elements in list
boolean add(E element); // add element at the end of the list
void add(int index, E element); // add element at given position
int indexOf(Object o); // returns index of object in list
... }

7. Question 2 Write the List<E> interface:
/** An ordered collection. The user can access elements by their
* integer index, and search for elements in the list. */
public interface List<E> extends Collection<E> {
E get(int index); // returns object at given position
E set(int index, E element); // sets element, returns old value
E remove(int index); // removes object at the given position
int size(); // returns number of elements in list
boolean add(E element); // add element at the end of the list
void add(int index, E element); // add element at given position
int indexOf(Object o); // returns index of object in list
... }

8. Question 2 Write the List<E> interface:
/** An ordered collection. The user can access elements by their
* integer index, and search for elements in the list. */
public interface List<E> extends Collection<E> {
E get(int index); // returns object at given position
E set(int index, E element); // sets element, returns old value
E remove(int index); // removes object at the given position
int size(); // returns number of elements in list
boolean add(E element); // add element at the end of the list
void add(int index, E element); // add element at given position
int indexOf(Object o); // returns index of object in list
... }

9. Question 2 Write the List<E> interface:
/** An ordered collection. The user can access elements by their
* integer index, and search for elements in the list. */
public interface List<E> extends Collection<E> {
E get(int index); // returns object at given position
E set(int index, E element); // sets element, returns old value
E remove(int index); // removes object at the given position
int size(); // returns number of elements in list
boolean add(E element); // add element at the end of the list
void add(int index, E element); // add element at given position
int indexOf(Object o); // returns index of object in list
... }

10. Question 2 Write the List<E> interface:
/** An ordered collection. The user can access elements by their
* integer index, and search for elements in the list. */
public interface List<E> extends Collection<E> {
E get(int index); // returns object at given position
E set(int index, E element); // sets element, returns old value
E remove(int index); // removes object at the given position
int size(); // returns number of elements in list
boolean add(E element); // add element at the end of the list
void add(int index, E element); // add element at given position
int indexOf(Object o); // returns index of object in list
... }

11. Question 3
Does Student inherit all the non-private methods of Person?
Does Student inherit all the non-private methods of GradeLevel?
Is Student required to provide all the methods of Person?
Is Student required to provide all the methods of GradeLevel?
Is Student a subclass of Person or GradeLevel (circle one)
public class Student extends Person implements GradeLevel {
yes no no
yes*

12. Question 4 Complete this implementation of the remove method.
public class MyArrayList<E> implements List<E> {
protected E[] data;
protected int size; …
public E remove(int index) {
if (index <0 || index >= size) {
throw new IndexOutOfBoundsException(“bad index “ + index); }

13. Question 4 Complete this implementation of the remove method.
public class MyArrayList<E> implements List<E> {
protected E[] data;
protected int size; …
public E remove(int index) {
if (index <0 || index >= size) {
throw new IndexOutOfBoundsException(“bad index “ + index); }
E returnValue = data[index];

14. Question 4 Complete this implementation of the remove method.
public class MyArrayList<E> implements List<E> {
protected E[] data;
protected int size; …
public E remove(int index) {
if (index <0 || index >= size) {
throw new IndexOutOfBoundsException(“bad index “ + index); }
E returnValue = data[index];
for (int i = index; i < size – 1; i++) {
data[i] = data[i + 1];

15. Question 4 Complete this implementation of the remove method.
public class MyArrayList<E> implements List<E> {
protected E[] data;
protected int size; …
public E remove(int index) {
if (index <0 || index >= size) {
throw new IndexOutOfBoundsException(“bad index “ + index); }
E returnValue = data[index];
for (int i = index; i < size – 1; i++) {
data[i] = data[i + 1];
size--;
return returnValue;

16. Question 5 Tell me (briefly) everything wrong with this method.
public static double sumProduct(Iterator<Integer> itter) {
double result = 0.0;
int index = 1;
for (Integer x : itter) {
result = x.doubleValue() * index;
index = index.next(); }
return index;
return result;

17. Question 5 Tell me (briefly) everything wrong with this method.
public static double sumProduct(Iterator<Integer> itter) {
double result = 0.0;
int index = 1;
for (Integer x : itter) {
result = x.doubleValue() * index;
index = index.next(); }
return index;
return result;

18. Question 5 Tell me (briefly) everything wrong with this method.
public static double sumProduct(Iterator<Integer> itter) {
double result = 0.0;
int index = 1;
for (Integer x : itter) {
result = x.doubleValue() * index;
index = index.next(); }
return index;
return result;

19. Question 5 Tell me (briefly) everything wrong with this method.
public static double sumProduct(Iterator<Integer> itter) {
double result = 0.0;
int index = 1;
for (Integer x : itter) {
result = x.doubleValue() * index;
index = index.next(); }
return index;
return result;

20. Question 5 Tell me (briefly) everything wrong with this method.
public static double sumProduct(Iterator<Integer> itter) {
double result = 0.0;
int index = 1;
for (Integer x : itter) {
result = x.doubleValue() * index;
index = index.next(); }
return index;
return result;

21. Question 5 Tell me (briefly) everything wrong with this method.
public static double sumProduct(Iterator<Integer> itter) {
double result = 0.0;
int index = 1;
for (Integer x : itter) {
result = x.doubleValue() * index;
index = index.next(); }
return index;
return result;

22. Question 6 What is the Big-O of the following code?
double result = 0.0;
for (int i = 5; i < 2n; i++) {
result = result * i;
for (int j = n – 2; j > 1; j--) {
int temp = j – i;
result += temp; }

23. Question 6 What is the Big-O of the following code?
double result = 0.0;
for (int i = 5; i < 2n; i++) { n – 6
result = result * i;
for (int j = n – 2; j > 1; j--) {
int temp = j – i;
result += temp; }

24. Question 6 What is the Big-O of the following code?
double result = 0.0;
for (int i = 5; i < 2n; i++) { n – 6
result = result * i;
for (int j = n – 2; j > 1; j--) { n - 3
int temp = j – i;
result += temp; }
(2n – 6) * (n – 3)

25. Question 6 What is the Big-O of the following code?
double result = 0.0;
for (int i = 5; i < 2n; i++) { n – 6
result = result * i;
for (int j = n – 2; j > 1; j--) { n - 3
int temp = j – i;
result += temp; }
2n2 – 9n - 18

26. Question 6 What is the Big-O of the following code?
double result = 0.0;
for (int i = 5; i < 2n; i++) { n – 5
result = result * i;
for (int j = n – 2; j > 1; j--) { n - 3
int temp = j – i;
result += temp; }
O(n2)

27. Question 7 The super class of all Java classes is
__________________________.
Object

28. Question 8
The Node class for a single-linked list has references to the data and to the next and previous Nodes? True of False. (circle one)

29. Question 9
Add the class variable(s) and implement the hasNext() and next() methods for this Linked List class:
public class MyLinkedList<E> implements List<E> {
protected LinkedNode<E> head; // singly-linked list …
private class MyIterator implements Iterator<E> {
public boolean hasNext() { }
public E next() { // may throw java.util.NoSuchElementException

30. Question 9
Add the class variable(s) and implement the hasNext() and next() methods for this Linked List class:
public class MyLinkedList<E> implements List<E> {
protected LinkedNode<E> head; // singly-linked list …
private class MyIterator implements Iterator<E> {
private LinkedNode<E> next;
public boolean hasNext() { }
public E next() { // may throw java.util.NoSuchElementException

31. Question 9
Add the class variable(s) and implement the hasNext() and next() methods for this Linked List class:
public class MyLinkedList<E> implements List<E> {
protected LinkedNode<E> head; // singly-linked list …
private class MyIterator implements Iterator<E> {
private LinkedNode<E> next;
public boolean hasNext() {
return next != null; }
public E next() { // may throw java.util.NoSuchElementException

32. Question 9
Add the class variable(s) and implement the hasNext() and next() methods for this Linked List class:
public class MyLinkedList<E> implements List<E> {
protected LinkedNode<E> head; // singly-linked list …
private class MyIterator implements Iterator<E> {
private LinkedNode<E> next;
public boolean hasNext() {
return next != null; }
public E next() { // may throw java.util.NoSuchElementException
if (!hasNext()) { throw new java.util.NoSuchElementException(); }

33. Question 9
Add the class variable(s) and implement the hasNext() and next() methods for this Linked List class:
public class MyLinkedList<E> implements List<E> {
protected LinkedNode<E> head; // singly-linked list …
private class MyIterator implements Iterator<E> {
private LinkedNode<E> next;
public boolean hasNext() {
return next != null; }
public E next() { // may throw java.util.NoSuchElementException
if (!hasNext()) { throw new java.util.NoSuchElementException(); }
E returnValue = next.data;
next = next.next;
return returnValue;

34. Question 10
Implement the following method using the bubble sort algorithm:
public static void bubbleSort(E[] data, Comparator<E> c) { }

35. Question 10
Implement the following method using the bubble sort algorithm:
public static void bubbleSort(E[] data, Comparator<E> c) {
int pass = 1;
boolean exchanged = false; }

36. Question 10
Implement the following method using the bubble sort algorithm:
public static void bubbleSort(E[] data, Comparator<E> c) {
int pass = 1;
boolean exchanged = false;
do {
} while (exchanged); }

37. Question 10
Implement the following method using the bubble sort algorithm:
public static void bubbleSort(E[] data, Comparator<E> c) {
int pass = 1;
boolean exchanged = false;
do {
exchanged = false;
for (int i = 0; i < data.length – pass; i++) { }
} while (exchanged);

38. Question 10
Implement the following method using the bubble sort algorithm:
public static void bubbleSort(E[] data, Comparator<E> c) {
int pass = 1;
boolean exchanged = false;
do {
exchanged = false;
for (int i = 0; i < data.length – pass; i++) {
if (c.compare(data[i], data[i + 1] > 0) { }
} while (exchanged);

39. Question 10
Implement the following method using the bubble sort algorithm:
public static void bubbleSort(E[] data, Comparator<E> c) {
int pass = 1;
boolean exchanged = false;
do {
exchanged = false;
for (int i = 0; i < data.length – pass; i++) {
if (c.compare(data[i], data[i + 1] > 0) {
exchanged = true;
E temp = data[i];
data[i] = data[i + 1];
data[i + 1] = temp; }
} while (exchanged);

40. Question 11
A Java interface is a(n) ______________________ between the interface designer and the programmer who codes a class that implements the interface. (circle one)
precondition
postcondition
message
contract

41. Question 12
When looping over a circularly linked list, how do you know when you have reached the end?
temp.next == head; or
temp == tail;