Arrays Chapter 7 Test Questions & Answers

Chapter 7: Arrays

Multiple Choice Questions:

1) In Java, array indexes always begin at ________________ .

a) -1

b) 0

c) 1

d) 2

e) you can declare an array to have any indexes you choose

2) Which of the following statements best describes this line of code?

numbers[5] = 12;

a) The value 12 is put into the numbers array at the location with index 5.

b) The value 5 is put into the numbers array at the location with index 12.

c) numbers is declared to be an array of 5 elements, each of which contains the number 12.

d) numbers is declared to be an array of 12 elements, each of which contains the number 5.

e) none of the above is correct

3) Which of the statements is true about the following code snippet?

int[] array = new int[25];

array[25] = 2;

a) The integer value 2 will be assigned to the last index in the array.

b) The integer value 25 will be assigned to the second index in the array.

c) The integer value 25 will be assigned to the third value in the array.

d) This code will result in a compile-time error.

e) This code will result in a run-time error.

4) What does this array contain?

String [] studentNames = new String[25];

a) names

b) students

c) studentNames

d) Strings

e) references to Strings

5) Which of the following array declarations are invalid?

a) int[] grades = new int[5];

b) int grades[] = new int[5];

c) int[] grades = { 91, 83, 42, 100, 77 };

d) all of the above are valid

e) none of the above are valid

6) Which of the following is a true statement?

a) Arrays are passed as parameters to methods like primitive types.

b) Arrays are passed as parameters to methods like object types.

c) Arrays cannot be passed as parameters to methods.

d) All of the above are true.

e) None of the above are true.

7) Suppose we have an array of String objects identified by the variable names. Which of the following for loops will not correctly process each element in the array.

a) for(int i = 0; i < names.length; i++)

b) for(String name : names)

c) for(int i = 0; i < names.length(); i++)

d) none of these will correctly process each element

e) all of these will correctly process each element

8) Which of the following statements will assign the first command-line argument sent into a Java program to a variable called argument?

a) argument = System.getFirstArgument();

b) argument = System.getArgument[1];

c) argument = System.getArgument[0];

d) argument = args[0];

e) argument = args[1];

9) Which of the following method declarations correctly defines a method with a variable length parameter list?

a) public int average(int[] list)

b) public int average(int ... list)

c) public int average(...)

d) public int average(int a, int b, int c, ...)

e) public int average(integers)

10) Which of the following is a valid declaration for a two-dimensional array?

a) int[][] matrix;

b) int[2] matrix;

c) int[]** matrix;

d) int[] matrix;

e) none of these are correct

11) Which of the following lines of code accesses the second element of the first array in a two-dimensional array of integers, numbers, and stores the result in a variable called num?

a) num = numbers[1][2];

b) num = numbers[0][1];

c) num = numbers.getElement(1, 2);

d) num = numbers.getElement(0, 1);

e) none of the above are correct

12) Which of the following are true about two-dimensional arrays?

a) Two-dimensional integer arrays cannot be initialized via an initializer list.

b) Two-dimensional arrays can only store up to 10 elements per array (or per row).

c) Two-dimensional arrays are not accessible using for loops.

d) Two-dimensional arrays cannot hold objects.

e) None of the above is true.

13) How do you determine the number of command-line arguments a program has?

a) The numArgs constant contains the number of command-line arguments.

b) The first member of the args array is the count of the number of command-line arguments.

c) The number of command-line arguments is the length of the args array.

d) The number of command-line arguments is one less than the length of the args array.

e) The number of command-line arguments is fixed and is 5.

14) What is the limit of the number of variable parameters that can be passed to a method that has a variable-length parameter list?

a) 5

b) 10

c) 16

d) less than 100

e) none of the above

15) Multi-dimensional arrays that contain arrays of different lengths in any one dimension are called _________________.

a) ragged arrays

b) static arrays

c) two-dimensional arrays

d) constant arrays

e) overloaded arrays

1) In Java, array indexes begin at 0 and end at one less than the length of the array.

2) If an array is declared to hold objects, none of the objects can have instance variables that are arrays.

3) An array declared as an int[] can contain elements of different primitive types.

4) The elements of a two-dimensional array are called rows and columns.

5) It is possible to store 11 elements in an array that is declared in the following way.

int[] array = new int[10];

6) If a program attempts to access an element outside of the range of the array indexes, a run-time error will occur.

7) An array cannot hold object types.

8) It is possible to send in data to a Java program via the command-line.

9) It is possible for a method to have a variable length parameter list, meaning that the method can take in any number of parameters of a specified data type.

10) In Java it is not possible to have arrays of more than two dimensions.

1) Explain how arrays are passed to methods as parameters.

2) Write the declaration for an array of doubles called averages that is initialized with an initializer list.

double[] averages = { 25.2, 36.18, 42.1, 30.5 };

3) Write the declaration for a two-dimensional array of integers that can be thought of as a table with three rows and three columns. Assign the value 3 to the cell that is in the second row and the third column.

int[][] table = new int[3][3];

table[1][2] = 3;

4) Write a loop that cycles through an array of String objects called names and prints them out, one per line.

for(int i = 0; i < names.length; i++)

System.out.println(names[i]);

for(String n : names)

System.out.println(n);

5) How do you determine how the elements of an array can be used in a program?

Refer to the array declaration to determine how the elements can be used. For example, if the array is declared with the type int [], then each element of the array is an individual int, and can be used in any way that is appropriate for an int. If the array is declared with a type that refers to a class, then the array elements are all references to objects of that class and can be used as such.

6) Student is a class that defines data fields and methods for an individual student. Write the declaration of an array named roster that can be used to reference 24 Student objects.

Student [] roster = new Student[24];

7) Write a method called doubleSize that accepts an integer array as a parameter and returns a reference to a new integer array that is twice as long and contains all of the elements of the first array in the same positions.

public int[] doubleSize(int[] originalArray) {

int[] newArray = int[originalArray.length*2];

for(int i = 0; i < originalArray.length; i++)

newArray[i] = originalArray[i];

return newArray;

}

8) Circle is a class that has data and methods related to circles. How many Circle objects are created by the following declaration?

Circle [] shapes = new Circle[12];

9) What is the purpose of command-line arguments to a Java program? How can they be used?

10) Write a method that takes in an arbitrary number of String objects, and then prints out all of them that have over 10 characters.

public void printLongStrings(String ... words) {

for(String w : words)

if(w.length() > 10)

System.out.println(w);

}

11) Write a method that takes in at least one integer and returns the largest of all integer parameters sent in.

public void largest(int first, int ... numbers) {

int currentLargest = first;

for(int num : numbers)

if(num > currentLargest)

currentLargest = num;

return currentLargest;

}

12) Write a method that accepts an array of integers as a parameter and returns a reference to an array that contains the even numbers in the array original array. The returned array should have a size equal to the number of even numbers in the original array.

public int[] getEvenArray(int[] numbers) {

int size = 0;

for(int i = 0; i < numbers.length; i++)

if(numbers[i]%2 == 0)

size++;

int[] evenArray = new int[size];

int evenArrayIndex = 0;

for(int i = 0; i < numbers.length; i++) {

if(numbers[i]%2 == 0) {

evenArray[evenArrayIndex] = numbers[i];

evenArrayIndex++;

}//end if

}//end for

}

13) Write a short program that accepts an arbitrary number of command line arguments, and prints out those containing the character 'z'.

public class PrintZArgs {

public static void main(String[] args) {

for(String s : args) {

boolean printed = false;

for(int i = 0; (i < s.length) && (!printed); i++)

if(s.charAt(i) == 'z') {

printed = true;

System.out.println(s);

} // end if

// end inner for loop

}//end foreach

}//end main

}//end class

14) Write a line of code that initializes a two-dimensional array of integers using an initializer list.

int[][] numbers = { {2,3},{4,5} };

15) The following declaration allocates space for how many double variables?

double [][][] temperatures = new double [10][20[]30];