Final Exam (part 2)

Question 1

What is the value in count after the following loop is executed?
int count = 0;
do {
System.out.println(“Welcome to Java”);
} while (count++ < 9);
System.out.println(count);

Answer 1

10

Question 2

Suppose the input for number is 9. What is the output from running the following program?

import java.util.Scanner;
public class Test{
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.println(“Enter an integer: “);
int number = input.nextInt();

  int i;

  boolean isPrime = true;
  for(i = 2; i < number && isPrime; i++) {
        if(number % i == 0) {
              isPrime = false;
        }
  }

  System.out.println("i is " + i);

  if (isPrime)
        System.out.println(number + " is prime");
  else
        System.out.println(number + " is not prime");   } }

Answer 2

i is 4 followed by 9 is not prime

Question 3

A break statement can be used only in a loop. T/F

Answer 3

false

Question 4

What is sum after the following loop terminates?

int sum = 0;
int item = 0;
do {
item++;
sum += item;
if (sum > 4) break;
}
while (item < 5);

Answer 4

6

Question 5

Suppose cond1 is a Boolean expression. When will this while condition be true?

while (cond1) …

Answer 5

in case cond1 is true

Question 6

Is the following loop correct?

for(; ; );

Answer 6

yes

Question 7

How many times will the following code print “Welcome to Java”?
int count = 0;
do {
System.out.println(“Welcome to Java”);
count++;
} while (count < 10);

Answer 7

10

Question 8

A variable declared in the for loop control can be used after the loop exits. T/F

Answer 8

False

Question 9

Each Java class must contain a main method. T/F

Answer 9

false

Question 10

You may have a return statement in a void method.

Answer 10

True

Question 11

(REPEAT QUESTION):
You may have a return statement in a void method.

Answer 11

True

Question 12

The signature of a method consists of _____.

Answer 12

method name and parameter list

Question 13

Each time a method is invoked, the system stores parameters and local variables in an area of memory, known as _______, which stores elements in last-in first-out fashion.

Answer 13

a stack

Question 14

Methods can be declared in any order in a class. T/F

Answer 14

true

Question 15

(char)(‘a’ + Math.random() * (‘z’ - ‘a’ + 1)) returns a random character _______.

Answer 15

between ‘a’ and ‘z’

Question 16

Analyze the following code.

public class Test {
public static void main (String[] args) {
System.out.println(m(2));
}

 public static int m (int num) {
      return num;
 }

 public static void m (int num) {
      System.out.println(num);
 } }

Answer 16

The program has a compile error because the two methods m have the same signature.

Question 17

Which of the following is correct to create an array?

int[] m = {1, 2, };
int[] m = {{1, 2}};
int[] m = {{1, 2}, {3, 4}};
int[] m = {1, 2, 3};

Answer 17

int[] m = {1, 2, 3};

Question 18

Which correctly creates an array of five empty Strings?

String[] a = new String[5];
String[] a = {“”, “”, “”, “”, “”};
String[5] a;
String[] a = new String[5]; for (int i = 0; i < 5; a[i++] = null);

Answer 18

String[] a = {“”, “”, “”, “”, “”};

Question 19

For the binarySearch method in Section 7.10.2, what is low and high after the first iteration of the while loop when invoking binarySearch(new int[]{1, 4, 6, 8, 10, 15, 20}, 11)?

Answer 19

low = 4
high = 26

Question 20

Assume int[] scores = {1, 20, 30, 40, 50}, what value does java.util.Arrays.binarySearch(scores, 3) return?

Answer 20

-2

Question 21

What is the output of the following code?

double[] myList = {1, 5, 5, 5, 5, 1};
double max = myList[0];
int indexOfMax = 0;
for (int i = 1; i < myList.length: i++) {
if (myList[i] > max) {
max = myList[i];
indexOfMax = i;
}
}

System.out.println(indexOfMax);

Answer 21

1

Question 22

When you pass an array to a method, the method receives ______.

Answer 22

the reference of the array

Question 23

Show the output of the following code:

public class Test {
public static void main(String[] args) {
int[] x = {1, 2, 3, 4, 5};
increase(x);

      int[] y = {1, 2, 3, 4, 5};
      increase(y[0]);

      System.out.println(x[0] + " " + y[0]);
 }

 public static void increase (int[] x) {
      for (int i = 0; i < x.length; i++)
           x[i]++;
 }

 public static void increase (int y) {
      y++;
 } }

Answer 23

2 1

Question 24

Which of the following are valid array declarations?

char[] charArray = new char[26];
int[] words = new words[10];
char[] charArray = “Computer Science”;
double[3] nums = {3.5, 35.1, 32.0};

Answer 24

char[] charArray = new char[26];

Question 25

What is the printout of the following code?

public class Test {
public static void main(String[ args) {
int[][][] data = {{{1, 2}, {3, 4}}, {{5, 6}, {7, 8}}};

      System.out.print(data[1][0][0]);
 } }

Answer 25

5

Question 26

Given the following declarations:
int[][] m = new int[5][6];

which of the following statements if true?

___The name m represents a two-dimensional array of 30 int values.
___m[2][4] represents the element stored in the 2nd row and the 4th column of m.
___m.length has the value 6.
___m[0].length has the value of 5.

Answer 26

The name m represents a two-dimensional array of 30 int values.

Question 27

What is the printout of the following program?

public class Test {
public static void main (String[] args) {
int[][] values = {{3, 4, 5, 1}, {33, 6, 1, 2}};

      int v = values[0][0];
      for (int[] list : values)
           for(int element : list)
                if (v > element)
                     v = element;
      System.out.print(v);
 } }

Answer 27

1

Question 28

int[][] matrix = new int[5][5];
for (int column = 0; column < matrix[4].length; column++);
matrix[4][column] = 10;

After the loop, the last column of matrix 10, 10, 10, 10, 10.
After the loop, the last row of matrix 10, 10, 10, 10, 10.
After the loop, the last row of matrix 0, 0, 0, 0, 0.
After the loop, the last row of matrix 0, 0, 0, 0, 0.
A syntax error, because column is not defined.

Answer 28

A syntax error, because column is not defined.

Question 29

What is the output of the following code?

public class Test {
public static void main(String[] args) {
int[][] matrix =
{{1, 2, 3, 4},
{4, 5, 6, 7),
{8, 9, 10, 11},
{12, 13, 14, 15}};

      for (int i = 0; i < 4; i++)
           System.out.print(matrix[i][1] + " ");
 } }

Answer 29

2 4 9 13

Question 30

Assume int[][][] x = new char[2][5][3], how many elements are in the array?

Answer 30

30

Question 31

Write a function public static void parseInt(int x), which prints all the digits of an int type argument x, one digit per line. For example, if int x = 38625, then the output should be in 5 lines as
3
8
6
2
5

Answer 31

public static void parseInt(int x) {
String n = Integer.toString(x);
for(int i = 0; i < n.length(); i++) {
System.out.println(n.charAt(i));
}
}

Question 32

Write method public static long factorial(int n) that take a positive integer n as input and return the product of 12…*n

Answer 32

public static long factorial(int n) {
int product = 1;
for(int i = 2; i <= n; i++) {
product *= i;
}
return product;
}

Question 33

Write a method public static initializeArray(int[] arr) to initialize a given int array named arr with random numbers between 25 and 150, inclusive.

Answer 33

public static initializeArray(int[] arr) {
for(int i = 0; i < arr.length; i++) {
arr[i] = (int)(25 + Math.random() * 150);
}
}

Question 34

Write public static int[] sums(int[][] arr) that returns an integer array, in which ith element is the sum of ith row of table arr.

Answer 34

public static int[] sums(int[][] arr) {
int[] intArray = new int[arr.length];
for(int i = 0; i < arr.length; i++) {
int sum = 0;
for(int j = 0; j < arr[i].length; j++) {
sum += arr[i][j];
}
intArray[i] = sum;
}
return intArray;
}

Question 35

Write public static boolean zeroDiagonal(int[][] arr) which returns true if the diagonal elements in table arr are all zeros.

Answer 35

public static boolean zeroDiagonal(int[][] arr) {
for(int i = 0; i < arr.length; i++) {
if(arr[i][i] != 0) return false;
}
return true;
}

Question 36

Write method public static int linearSearch(int[] arr, int key) which returns the largest index such that arr[index] matches the key. If there is match, returns -1.

Answer 36

public static int linearSearch(int[] arr, int key) {
int bigIndex = -1;
for(int i = 0; i < arr.length; i++) {
if(arr[i] == key) bigIndex = i;
}
return bigIndex;
}

Question 37

Write a while (or for) statement to print all the digits of an int type variable x reversely, one digit per line. For example, if int x = 38625, then the output should be in 5 lines as
5
2
6
8
3

Answer 37

while(x > 0) {
System.out.println(x % 10);
x -= x % 10;
x /= 10;
}

Question 38

Write a while (or do-while loop) loop to get user’s input of test scores. Keep track the total score and number of scores entered. When user enter -1, the loop finishes and prints out the average score. Declare and initialize variables as needed.

Answer 38

Scanner input = new Scanner(System.in);
int userScore = 0;
int totalScore = 0;
int numberOfScores = 0;
while(userScore != -1) {
userScore = input.nextInt();
if(userScore == -1) break;
totalScore += userScore;
numberOfScores++;
}
double average = ((double)totalScore) / numberOfScores;
System.out.println(average);