Practice Midterm Sarah

Question 1

If you declare an array int[] list = {5, 2, 3, 4}, the highest index in the array list is

Answer 1

list[3];

Question 2

How many times is the println statement executed?

for (int i = 0; i < 10; i++)
for (int j = 0; j < 2; j++)
System.out.println(i * j);

Answer 2

20

Question 3

Analyze the following code

boolean[] x = new boolean[3];
System.out.println("x[0] is " + x[0]);

Answer 3

c. The program runs fine and displays x[0] is false.

Question 4

What is 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(y[0] + " " + x[0]);   }

public static void increase(int[] x) {
for (int i = 0; i < x.length; i++)
x[i] += 10;
}

public static void increase(int y) {
y += 10;
}
}

Answer 4

d. 1 11

Question 5

What is the output of the following code?

public class Test {
public static void main(String[] args) {
int[][] matrix =
{{1, 2, 3, 4},
{5, 6, 7, 8},
{9, 10, 11, 12},
{13, 14, 15, 16}};

for (int i = 0; i < matrix.length; i++)
  System.out.print(matrix[2][i] + " ");   } }

Answer 5

b. 9 10 11 12

Question 6

Write a method header (not the bodies) for the following:
a) Return a sales commission, given the month and year

Answer 6

public static double getSalesCommission(int month, int year)

Question 7

Write a method header (not the bodies) for the following:
b) Display the calendar for a month, given the month and year.

Answer 7

public static void displayCalendar(int month, int year)

Question 8

Write a method header (not the bodies) for the following:c) Return the square root of a number

Answer 8

public static double squareRoot(double num)

Question 9

Write a method header (not the bodies) for the following:
d) Test whether a number is even, and return true if it is.

Answer 9

public static boolean isEven(int num)

Question 10

What is method overloading?

Answer 10

Multiple methods can have the same name as long as the parameters are different.

Question 11

What property do you need before you can perform a binary search on an array?

Answer 11

The array needs to be sorted in increasing order.

Question 12

Write the line of code to invoke a method named printBoard that does not have any parameters, and does not return anything.

Answer 12

printBoard();

Question 13

Declare and instantiate a 3 dimensional array named fun with dimensions 30 by 10 by 5.

Answer 13

int[][][] fun = new int[30][10][5];

Question 14

Calculate the sum of all the elements in an array of doubles named temperatures

Answer 14

double sum = 0;
for(int i = 0; i < temperature.length; i++){
sum += temperature[i];
}

Question 15

Write a method that takes in a string and returns the number of special characters that aren’t letters or digits.

Answer 15

public static int numSpecCharacters(String ch){
int count = 0;
for(int i = 0; i < ch.length(); i++){
char x = ch.charAt(i);
if(!Character.isLetterOrDigit(x)){
count++;
}
}
return count;
}

Question 16

Write a code segment that would display the following output using nested for loops:
1
1 2
1 2 3
1 2 3 4

Answer 16

for(int i = 1; i <= 4; i++){
for (int j = 1; j <= i; j++){
System.out.print(j + “ “);
}
System.out.println();
}

Question 17

Write a method that takes an int array parameter and returns the number that occurred the most frequently in that array. The array will only contain numbers in the range of 1 to 5 inclusive.
Example 1: Input: 4 5 1 2 3 4 5 4 4
Output: 4

Example 2: Input: 3 3 3 4 4 4 3 2 1 5 3
Output: 3

Answer 17

public static int mostFrequent(int[] arr){
int maxCount = 0;
int maxNum = 0;
for (int i = 1; i <= 5; i++){
int count = 0;
for(int j = 0; j < arr.length; j++){
if(arr[j] == i){
count++;
}
}
if (count > maxCount){
maxCount = count;
maxNum = i;
}
}
return maxNum;
}

Question 18

Array input values

Answer 18

Scanner input = new Scanner(System.in);
System.out.println(“How many elements in the array: “);
int n = input.nextInt();

    double[] userArray = new double[n];

    for (int i = 0; i < userArray.length; i++){
        System.out.println("Enter a double number: ");

        userArray[i] = input.nextDouble(); }

Question 19

write a for loop to assign a value to all the elements in the array

Answer 19

//write a for loop to access and println all the elements in the array

    for (int i = 0; i < userArray.length; i++){
        System.out.println(userArray[i] + " ");
    }

Question 20

//create a new array with randon values

Answer 20

double[] randArray = new double[100];
for(int i = 0; i < randArray.length; i++){
randArray[i] = Math.random() * 100;
}
for (int i = 0; i < randArray.length; i++){
System.out.println(randArray[i] + “ “);
}

Question 21

//sum of all the elements in the array

Answer 21

double total = 0;
for (int i = 0; i < randArray.length; i++){
System.out.println(randArray[i] + “ “);
total += randArray[i];
}

Question 22

//find the largest number in the array

Answer 22

System.out.println(total);
double largest = randArray[0];
for (int i = 1; i < randArray.length; i++){
if (randArray[i] > largest){
largest = randArray[i];
}
}

Question 23

//set the element values to indeces

Answer 23

System.out.println(largest);
int[] intArray = new int[10];
for (int i = 0; i < intArray.length; i++){
intArray[i] = i;

Question 24

//shuffling elements in the Array

Answer 24

//shuffling elements in the Array
for (int i = 0; i < intArray.length; i++){
int randIndex = (int)(Math.random() * intArray.length);
//swap
int temp = intArray[1];
intArray[i] = intArray[randIndex];
intArray[randIndex] = temp;
}
//println elements for the array
for (int i = 0; i < intArray.length; i++){
System.out.println(intArray[i] + “ “);
}
System.out.println();

    //set the element values to indices
    for (int i = 0; i < intArray.length; i++){
        intArray[i] = i;
    }

Question 25

//shift all elements to the “left”

Answer 25

int temp = intArray[0];
for(int i = 1; i < intArray.length; i++){
intArray[i - 1] = intArray[i];
}
intArray[intArray.length -1] = temp;

    //println elements in array
    for (int i = 0; i < intArray.length; i++){
        System.out.println(intArray[i] + " ");
    }
    System.out.println();
    
    //println elements in array shifting one to the right 
    //make sure you are 
    temp = intArray[intArray.length -1];
    for (int i = intArray.length-1; i > 0; i--){
        intArray[i] = intArray[i-1];
    }
    intArray[0] = temp;
    //println elements in array
    for (int i = 0; i < intArray.length; i++){
        System.out.println(intArray[i] + " ");
    }
    System.out.println();

Question 26

Reverse array

Answer 26

public class ReverseArray{
public static void main(String[] args){
int[] list1 = {1,2,3,4,5};
int[] list2 = reverse(list1);
CopyArrays.printArray(list1);
CopyArrays.printArray(list2);
}
//return a new array with elements reversed
public static int[] reverse (int[] arr){
int[] reverse = new int[arr.length];
for(int i = 0, j = arr.length-1; i<arr.length; i++, j–){
reverse[j] = arr[i];
}
return reverse;
}
}

Question 27

Random Shuffle

Answer 27

public class randomShuffle{
public static void main(String[] args){

    double[] myList = {100, 90, 80, 70, 60, 50, 40, 30, 20, 10};
    for (int i = 0; i < myList.length; i++){
        //generate an index j randomly
        int j = (int)(Math.random() * myList.length);

        //swap myList[i] with myList[j]
        double temp = myList[i];
        myList[i] = myList[j];
        myList[j] = temp;
    }
    for(double i : myList){
        System.out.println(i);
    }
} }

Question 28

Random Shuffle

Answer 28

public class randomShuffle{
public static void main(String[] args){

    double[] myList = {100, 90, 80, 70, 60, 50, 40, 30, 20, 10};
    for (int i = 0; i < myList.length; i++){
        //generate an index j randomly
        int j = (int)(Math.random() * myList.length);

        //swap myList[i] with myList[j]
        double temp = myList[i];
        myList[i] = myList[j];
        myList[j] = temp;
    }
    for(double i : myList){
        System.out.println(i);
    }
} }