Question 1

In Java an array can only store one type of data.

Accepted Answer

Java arrays can only store elements of a single data type. This means that all elements in the array must be of the same data type, whether that be integers, strings, objects, etc.

Question 2

The "off-by-one" error associated with arrays arises because
A) the first array index is 0 and programmers may start at index 1 or may use a loop that goes one index too far
B) the last array index is at length+1 and loops may only iterate to length, missing one
C) the last array index is at length-1 and loops may go one too far
D) programmers write a loop that goes from 0 to length-1 whereas the array actually goes from 1 to length
E) None of these; the "off-by-one" error has nothing to do with arrays

Accepted Answer

In most programming languages, the first index of an array is 0, but programmers may mistakenly start indexing at 1 or use a loop that iterates one too far, resulting in an "off-by-one" error.

Question 3

A ragged array is a multidimensional array whose initial indices don't all start at zero.

Accepted Answer

A ragged array is a multidimensional array where the sub-arrays can have different lengths, not necessarily related to their starting indices.

Question 4

Java arrays can store primitive types and Strings but cannot store any type of Object other than Strings.

Accepted Answer

Java arrays can store any type of Object, including Strings and other custom objects.

Question 5

Code Example Ch 08-1
Assume an int array, values, that is filled to capacity with the following values:
|18 | 9 | 4 | 12 | 2 | 6 | 8 | 
-Refer to Code Example Ch 08-1: What is returned by values.length?
A) 0
B) 5
C) 6
D) 7
E) 18

Accepted Answer

The length of an array is the total number of elements it can hold. In this case, there are 7 elements (18, 9, 4, 12, 2, 6, 8), so values.length returns 7.

Question 6

A Java main method uses the parameter (String[] variable) so that a user can run the program and supply command-line parameters. Since the parameter is a String array, however, the user does not have to supply any parameters.

Accepted Answer

This is because the String array parameter is optional, and the user can run the program without supplying any command-line parameters. The program must handle this possibility and include appropriate default behavior for when no parameters are given.

Question 7

Code Example Ch 08-1
Assume an int array, values, that is filled to capacity with the following values:
|18 | 9 | 4 | 12 | 2 | 6 | 8 | 
-Refer to Code Example Ch 08-1: Which of the following loops would adequately add 1 to each element stored in values?
A) for (j=1; j<values.length; j++) values[j]++;
B) for (j=0; j<values.length; j++) values[j]++;
C) for (j=0; j<=values.length; j++) values[j]++;
D) for (j=0; j<values.length-1; j++) values[j]++;
E) for (j=1; j<values.length-1; j++) values[j]++;

Accepted Answer

Option B is the best choice as it starts the loop at the first element (index 0) and goes through every element in the array up to the last element (index values.length-1). It then adds 1 to each element using the post-increment operator (++). Option A starts the loop at index 1, thus missing the first element. Option C uses the less than or equal to operator, which will cause an ArrayIndexOutOfBoundsException error since the loop will try to access one element past the end of the array. Option D starts the loop at index 0 but only goes through every element up to the second to last element, thus missing the last element. Option E starts the loop at index 1, thus missing the first element, and also only goes through every element up to the second to last element, thus missing the last element.

Question 8

So long as one is only accessing the elements of an ArrayList, its efficiency is about the same as that of an array. It's only when one begins to insert or remove elements towards the front portion of an ArrayList that its efficiency deteriorates.

Accepted Answer

This is because ArrayList uses a dynamic array implementation, which allows for constant time access of elements using their index value, just like an array. However, if elements are added or removed from the front of the ArrayList, all the subsequent elements have to be shifted to make room or close the gap, which takes O(n) time, where n is the number of remaining elements. This is less efficient compared to adding or removing elements from the end of the ArrayList, which can be done in constant time or O(1).

Question 9

Arrays have a built-in toString method that returns all the elements in the array as one String with 
 inserted between each element.

Accepted Answer

The built-in toString method for arrays returns a single String with each element of the array separated by commas (,) and not by newline characters (
).

Question 10

Code Example Ch 08-1
Assume an int array, values, that is filled to capacity with the following values:
|18 | 9 | 4 | 12 | 2 | 6 | 8 | 
-Refer to Code Example Ch 08-1: What will the following statement do? System.out.println(values[7]);
A) output 7
B) output 18
C) output nothing
D) cause an ArrayOutOfBoundsException to be thrown
E) cause a syntax error

Accepted Answer

The array `values` has indices from 0 to 6 (inclusive), so trying to access `values[7]` will exceed the bounds of the array, causing an `ArrayOutOfBoundsException` to be thrown.

Question 11

In Java, arrays are
A) primitive data types
B) objects
C) interfaces
D) primitive data types if the type stored in the array is a primitive data type and objects if the type stored in the array is an object
E) Strings

Accepted Answer

Arrays in Java are objects. They are instances of a class that provides certain methods and properties to work with the data stored in the array. Despite the fact that arrays have a dedicated syntax in Java, they are not primitive data types but rather objects.

Question 12

Just as arrays can only have a fixed number of elements, set at the time the array is declared, a parameter list also can only have a fixed number of elements, set at the time a method is declared.

Accepted Answer

Parameter lists can include variable arguments (varargs) allowing a method to accept zero or more arguments of a specified type, making the number of elements flexible.

Question 13

In a two-dimensional array, both dimensions must have the same number of elements, as in my_array[10][10].

Accepted Answer

In a two-dimensional array, the number of elements in each dimension can be different, as long as it is specified during declaration. For example, my_array[5][10] is a valid two-dimensional array.

Question 14

An array index cannot be a float, double, boolean, or String.

Accepted Answer

An array index can only be an integer.

Question 15

Given the following statement, where CD is a previously defined class, then mycollection[5] is a CD object.
CD[] mycollection = new CD[200];

Accepted Answer

The statement creates an array of 200 CD objects and assigns it to the variable "mycollection". Therefore, accessing the 5th element of the array with "mycollection[5]" would retrieve a CD object.

Question 16

Code Example Ch 08-1
Assume an int array, values, that is filled to capacity with the following values:
|18 | 9 | 4 | 12 | 2 | 6 | 8 | 
-Refer to Code Example Ch 08-1: What is returned by values[3]?
A) 9
B) 12
C) 2
D) 6
E) 3

Accepted Answer

The answer of Code Example Ch 08-1
Assume an int array,...

Question 17

It is possible to sort an array of int, float, double or String, but not an array of an Object class.

Accepted Answer

It is possible to sort an array of an Object class by implementing the Comparable or Comparator interface and overriding the compareTo or compare method.

Question 18

Which of the following is a legal way to declare and instantiate an array of ten Strings?
A) String s = new String(10);
B) String[10] s = new String;
C) String[] s = new String[10];
D) String s = new String[10];
E) String[] s = new String; e

Accepted Answer

The syntax for declaring and instantiating an array of Strings is to use the square brackets [] after the data type String followed by the size of the array in square brackets [] and then use the keyword new to allocate memory for the array. Therefore, option C is the correct way to declare and instantiate an array of ten Strings. Option A is incorrect because it creates a single String object with the value "10". Option B is incorrect because it declares an array of Strings but does not allocate memory for it. Option D is incorrect because it assigns an array of Strings to a single String variable which is not allowed. Option E is incorrect because it declares an array of Strings but does not allocate memory for it.

Question 19

An array, when instantiated, is fixed in size but an ArrayList can dynamically change in size when new elements are added to it.

Accepted Answer

Arrays have a fixed length that cannot be changed once they are instantiated, while ArrayLists can grow or shrink dynamically to accommodate new elements.

Question 20

A command-line argument is data that is included on the command line when the interpreter is invoked to execute the program.

Accepted Answer

This is true. Command-line arguments are additional input values that can be passed to a program when it is executed from the terminal/command line. These arguments can be used by the program to modify its behavior or perform specific tasks based on user input.

Quiz 8: Arrays

In Java an array can only store one type of data.

The "off-by-one" error associated with arrays arises because

A ragged array is a multidimensional array whose initial indices don't all start at zero.

Java arrays can store primitive types and Strings but cannot store any type of Object other than Strings.

Code Example Ch 08-1 Assume an int array, values, that is filled to capacity with the following values: |18 | 9 | 4 | 12 | 2 | 6 | 8 | -Refer to Code Example Ch 08-1: What is returned by values.length?

A Java main method uses the parameter (String[] variable) so that a user can run the program and supply command-line parameters. Since the parameter is a String array, however, the user does not have to supply any parameters.

Code Example Ch 08-1 Assume an int array, values, that is filled to capacity with the following values: |18 | 9 | 4 | 12 | 2 | 6 | 8 | -Refer to Code Example Ch 08-1: Which of the following loops would adequately add 1 to each element stored in values?

So long as one is only accessing the elements of an ArrayList, its efficiency is about the same as that of an array. It's only when one begins to insert or remove elements towards the front portion of an ArrayList that its efficiency deteriorates.

Arrays have a built-in toString method that returns all the elements in the array as one String with \n inserted between each element.

Code Example Ch 08-1 Assume an int array, values, that is filled to capacity with the following values: |18 | 9 | 4 | 12 | 2 | 6 | 8 | -Refer to Code Example Ch 08-1: What will the following statement do? System.out.println(values[7]) ;

In Java, arrays are

Just as arrays can only have a fixed number of elements, set at the time the array is declared, a parameter list also can only have a fixed number of elements, set at the time a method is declared.

In a two-dimensional array, both dimensions must have the same number of elements, as in my_array[10][10].

An array index cannot be a float, double, boolean, or String.

Given the following statement, where CD is a previously defined class, then mycollection[5] is a CD object. CD[] mycollection = new CD[200];

Code Example Ch 08-1 Assume an int array, values, that is filled to capacity with the following values: |18 | 9 | 4 | 12 | 2 | 6 | 8 | -Refer to Code Example Ch 08-1: What is returned by values[3]?

It is possible to sort an array of int, float, double or String, but not an array of an Object class.

Which of the following is a legal way to declare and instantiate an array of ten Strings?

An array, when instantiated, is fixed in size but an ArrayList can dynamically change in size when new elements are added to it.

A command-line argument is data that is included on the command line when the interpreter is invoked to execute the program.