Question 1

Which one of the following statements is a valid initialization of an array named somearray of ten elements?

Accepted Answer

Option A initializes an array named "somearray" with ten elements containing the values from 0 to 9. Option B also initializes an array with ten elements, but includes an additional element with the value of 10, which was not specified in the question. Option C is not valid syntax for initializing an array, and option D places the size declaration in the wrong location.

Question 2

Consider the following line of code:
Int[] somearray = new int[30];
Which one of the following options is a valid line of code for displaying the twenty-eighth element of somearray?

Accepted Answer

In Java, array indices start at 0, so the twenty-eighth element is at index 27. The correct syntax for accessing an array element is using square brackets, hence somearray[27].

Question 3

What is the output of the given code snippet?
Int[] mynum = new int[5];
For (int i = 1; i < 5; i++)
{
Mynum[i] = i + 1;
System.out.print(mynum[i]);
}

Accepted Answer

The loop starts with i=1 and goes up to i=4. For each iteration, mynum[i] is set to i+1, resulting in the output 2345.

Question 4

Suppose you wish to write a method that returns the sum of the elements in the partially filled array myArray. Which is a reasonable method header?

Accepted Answer

The method needs to know both the array and the number of elements that are actually filled (currSize) to correctly compute the sum.

Question 5

Complete the following code snippet with the correct enhanced for loop so it iterates over the array without using an index variable. String[] arr = { "abc", "def", "ghi", "jkl" };
___________________
{
System.out.print(str);
}

Accepted Answer

The enhanced for loop syntax is "for (Type element : array)" where "Type" is the data type of the array elements, "element" is the variable to hold each element, and "array" is the array to iterate over.

Question 6

Which statements about the enhanced for loop are true for arrays of primitve data?
I. It is suitable for all array algorithms
II. It does not allow the contents of the array to be modified
III. It does not require the use of an index variable

Accepted Answer

The enhanced for loop does not allow modification of array elements and does not require an index variable, but it is not suitable for all array algorithms, especially those that require modifying elements or accessing specific indices.

Question 7

What is the result of executing this code snippet?
Int[] marks = { 90, 45, 67 };
For (int i = 0; i <= 3; i++)
{
System.out.println(marks[i]);
}

Accepted Answer

The loop iterates from 0 to 3, but the array only has indices 0 to 2. Accessing marks[3] causes an ArrayIndexOutOfBoundsException.

Question 8

Which one of the following statements is correct for the given code snippet?
Int[] number = new int[3]; // Line 1
Number[3] = 5; // Line 2

Accepted Answer

Line 2 causes a bounds error because arrays in Java are zero-indexed, so valid indices for an array of size 3 are 0, 1, and 2. Index 3 is out of bounds.

Question 9

In a partially filled array, the number of slots in the array that are not currently used is

Accepted Answer

The number of unused slots in a partially filled array is calculated by subtracting the number of elements currently in the array from the total length of the array.

Question 10

Which one of the following statements is correct about the given code snippet?
Int[] somearray = new int[6];
For (int i = 1; i < 6; i++)
{
Somearray[i] = i + 1;
}

Accepted Answer

The for loop starts with i=1, so it skips initializing the first element (index 0) and initializes elements from index 1 to 5.

Question 11

The enhanced for loop

Accepted Answer

The enhanced for loop, also known as the "for-each" loop, is designed to iterate over all elements in an array or any Iterable collection, making it convenient for traversing all elements.

Question 12

When the order of the elements is unimportant, what is the most efficient way to remove an element from an array?

Accepted Answer

When the order of the elements is unimportant, replacing the element to be deleted with the last element in the array is the most efficient way to remove it. This is because we do not need to move any of the remaining elements in the array, whereas deleting an element would require shifting all the elements after it down by one index. This approach has a time complexity of O(1) and is the most efficient.

Question 13

What is the output of the following code snippet?
Int[] myarray = { 10, 20, 30, 40, 50 };
System.out.print(myarray[2]);
System.out.print(myarray[3]);

Accepted Answer

The code accesses the elements at index 2 and 3 of the array, which are 30 and 40, respectively, and prints them consecutively.

Question 14

What is the valid range of index values for an array of size 10?

Accepted Answer

In most programming languages, array indices start at 0, so for an array of size 10, the valid index range is 0 to 9.

Question 15

When an array myArray is only partially filled, how can the programmer keep track of the current number of elements?

Accepted Answer

Maintaining a companion variable that stores the current number of elements is the best choice as it allows the programmer to keep track of the actual number of elements in the array even if the array is only partially filled. Accessing myArray.length() or myArray.length() - 1 may not give the correct number of elements as the length of the array remains fixed regardless of how many elements are actually stored. Accessing myArray.currentElements() is not a valid method in Java.

Question 16

What is displayed after executing the given code snippet?
Int[] mymarks = new int[10];
Int total = 0;
Scanner in = new Scanner(System.in);
For (int cnt = 1; cnt <= 10; cnt++)
{
System.out.print("Enter the marks: ");
Mymarks[cnt] = in.nextInt();
Total = total + mymarks[cnt];
}
System.out.println(total);

Accepted Answer

The code causes a bounds error because array indices in Java are zero-based, so accessing `mymarks[cnt]` with `cnt` starting from 1 will result in an `ArrayIndexOutOfBoundsException`.

Question 17

Which code snippet prints out the elements in a partially filled array of integers?

Accepted Answer

The loop in option C uses a variable `currLength` to iterate, which is typically used to track the number of elements in a partially filled array.

Question 18

Which statements are true about the buffer overrun attack launched over the Internet in 1988?
I. The buffer overrun exploited a program that was written in C running on the Unix operating system
II. The Java programming language generates a run-time exception when buffer overrun occurs
III. In recent years computer attacks have lessened

Accepted Answer

The 1988 Internet worm exploited a buffer overrun in a C program on Unix. Java, introduced later, handles buffer overruns with exceptions. Computer attacks have not lessened in recent years.

Question 19

What is the result of the following code? for (double element : values)
{
Element = 0;
}

Accepted Answer

The code attempts to set each element of the array 'values' to zero, but it mistakenly uses 'Element' instead of 'element', which is a new variable and does not affect the 'values' array.

Question 20

Identify the correct statement for defining an integer array named numarray of ten elements.

Accepted Answer

To define an integer array named numarray of ten elements, we need to use the int[] keyword to specify the data type of the array elements, followed by the name of the array (numarray), and then the number of elements in the array (10). The correct syntax is: int[] numarray = new int[10]; Option A creates an array with 9 elements, option C uses incorrect syntax, and option D uses incorrect syntax.

Quiz 7: Arrays and Array Lists

Which one of the following statements is a valid initialization of an array named somearray of ten elements?

Consider the following line of code: Int[] somearray = new int[30]; Which one of the following options is a valid line of code for displaying the twenty-eighth element of somearray?

What is the output of the given code snippet? Int[] mynum = new int[5]; For (int i = 1; i < 5; i++) { Mynum[i] = i + 1; System.out.print(mynum[i]) ; }

Suppose you wish to write a method that returns the sum of the elements in the partially filled array myArray. Which is a reasonable method header?

Complete the following code snippet with the correct enhanced for loop so it iterates over the array without using an index variable. String[] arr = { "abc", "def", "ghi", "jkl" }; ___________________ { System.out.print(str) ; }

Which statements about the enhanced for loop are true for arrays of primitve data? I. It is suitable for all array algorithms II. It does not allow the contents of the array to be modified III. It does not require the use of an index variable

What is the result of executing this code snippet? Int[] marks = { 90, 45, 67 }; For (int i = 0; i <= 3; i++) { System.out.println(marks[i]) ; }

Which one of the following statements is correct for the given code snippet? Int[] number = new int[3]; // Line 1 Number[3] = 5; // Line 2