Question 1

When an integer literal is added to an array list declared as ArrayList<Integer>, Java performs:
A) casting
B) trimming
C) auto-boxing
D) auto-fixing

Accepted Answer

When an integer literal is added to an ArrayList<Integer>, Java performs auto-boxing, which is the process of converting a primitive data type to its corresponding wrapper class object. In this case, the integer literal is automatically boxed into an Integer object before being added to the ArrayList.

Question 2

What is the output of the code snippet below?
Int[][] arr =
{
{ 1, 2, 3, 0 },
{ 4, 5, 6, 0 },
{ 0, 0, 0, 0 }
};
Int val = arr[1][2] + arr[1][3];
System.out.println(val);
A) 5
B) 6
C) 7
D) 9

Accepted Answer

arr[1][2] refers to the element at the second row and third column, which has a value of 6. arr[1][3] refers to the element at the second row and fourth column, which has a value of 0. Therefore, val is equal to 6 + 0, which is 6. Thus, the correct output should be 6.

Question 3

Which statement is true about the code snippet below? ArrayList names = new ArrayList(); Names.add("John"); Names.add("Jerry"); ArrayList friends = new ArrayList(names); Names.add("Harry"); A) The final size of names is 2; the final size of friends is 3 B) The final size of names is 3; the final size of friends is 2 C) The final size of names is 3; the final size of friends is 3 D) Compilation error

Accepted Answer

The answer of Which statement is true about the code...

Question 4

What is the output of the following statements? ArrayList names = new ArrayList(); Names.add("Bob"); Names.add(0, "Ann"); Names.remove(1); Names.add("Cal"); Names.set(2, "Tony"); For (String s : names) { System.out.print(s + ", "); } A) Cal, Bob, Ann B) Ann, Bob C) Ann, Cal, Tony D) Array list bound error

Accepted Answer

The answer of What is the output of the following...

Question 5

Which statement is true about the code snippet below? ArrayList names = new ArrayList(); Names.add("John"); Names.add("Jerry"); ArrayList friends = new ArrayList(names); Friends.add("Harry"); A) The final size of names is 2; the final size of friends is 3 B) The final size of names is 3; the final size of friends is 2 C) The final size of names is 3; the final size of friends is 3 D) Compilation error

Accepted Answer

The code creates an ArrayList named "names" and adds two Strings to it. Then, it creates a new ArrayList named "friends" using "names" as a parameter. This effectively clones "names" into "friends". Finally, the code adds a third String to "friends". Therefore, the final size of "names" remains 2 while the final size of "friends" is 3.

Question 6

What is true about the following code snippet?
Public static double[] fillWithRandomNumbers(double[] values)
{
Double[] numbers = new double[values.length];
For (int i = 0; i < numbers.length; i++)
{
Numbers[i] = Math.random();
}
Return Arrays.copyOf(numbers, numbers.length);
}
Public static void main(String[] args)
{
Double[] num = new double[20];
Num = fillWithRandomNumbers(num);
}
A) The code has a run-time error
B) The code has a compilation error
C) The code has a logic error
D) The code is inefficient

Accepted Answer

The answer of What is true about the following code...

Question 7

What is the output of the following code?
Int[][] counts =
{
{ 0, 0, 1 },
{ 0, 1, 1, 2 },
{ 0, 0, 1, 4, 5 },
{ 0, 2 }
};
System.out.println(counts[3].length);
A) 2
B) 3
C) 4
D) 5

Accepted Answer

The answer of What is the output of the following...

Question 8

How many elements can be stored in a two-dimensional 5 by 6 array?
A) 5
B) 6
C) 11
D) 30

Accepted Answer

To find the total number of elements in a 2D array, we need to multiply the number of rows by the number of columns. Therefore, the number of elements in a 5 by 6 array is 5 x 6 = 30. So, the best choice is D.

Question 9

Consider the following code snippet, where the array lists contain elements that are stored in ascending order: ArrayList list1 = new ArrayList(); ArrayList list2 = new ArrayList(); ) . . Int count = 0; For (int i = 0; i < list1.size() && i < list2.size(); i++) { If (list1.get(i) == list2.get(i)) { Count++; } } Which one of the following descriptions is correct for the given code snippet? A) The code snippet finds the highest value out of the two array lists. B) The code snippet finds the lowest value out of the two array lists. C) The code snippet compares the values of two array lists and stores the count of total matches found. D) The code snippet adds the values of the two array lists.

Accepted Answer

The code snippet compares the values of two array lists using a for loop and stores the count of total matches found in the variable 'count'. It does not find the highest or lowest value out of the two lists, nor does it add the values of the two lists together.

Question 10

Consider the following code snippet: Public static void main(String[] args) { ArrayList names = new ArrayList(); Names.add("John"); Names.add("Jerry"); Names.add("Janet"); ArrayList names = reverse(names); } Public static ArrayList reverse(ArrayList names) { ArrayList result = new ArrayList(); For (int i = names.size() - 1; i >= 0; i--) { Result.add(names.get(i)); } Return result; } Which statement is true after the main method is executed? A) names contains "Janet", "Jerry", "John" in this order B) names contains "John", "Jerry", "Janet" in this order C) reverse method has a bound error D) Compilation error due to the return statement in reverse method

Accepted Answer

The code has a compilation error because the return statement in the reverse method is incorrectly formatted. It should be "return result;" instead of "Return <String>result;". Additionally, there are issues with case sensitivity in variable names and method calls.

Question 11

What is the output of the code snippet below?
Int[][] numarray =
{
{ 8, 7, 6 },
{ 0, 0, 0 }
};
System.out.print(numarray[0][0]);
System.out.print(numarray[1][0]);
A) 00
B) 87
C) 80
D) 08

Accepted Answer

The answer of What is the output of the code...

Question 12

Which statement is true about the code snippet below? ArrayList names = new ArrayList(); Names.add("John"); Names.add("Jerry"); ArrayList friends = names; Friends.add("Harry"); A) The final size of names is 2; the final size of friends is 3 B) The final size of names is 3; the final size of friends is 2 C) The final size of names is 3; the final size of friends is 3 D) Compilation error

Accepted Answer

The code first declares and initializes an ArrayList of strings called names. It adds two strings, "John" and "Jerry", to this ArrayList. Then, the code creates a new ArrayList of strings called friends and assigns it to the value of names. This means that both names and friends refer to the same ArrayList object in memory.

Next, the code adds the string "Harry" to the friends ArrayList. Since friends and names refer to the same ArrayList, this also adds "Harry" to the names ArrayList. Therefore, the final size of both names and friends is 3. Option C is correct.

Question 13

Consider the following code snippet:
Int[][] arr =
{
{ 1, 2, 3, 0 },
{ 4, 5, 6, 0 },
{ 0, 0, 0, 0 }
};
Int[][] arr2 = arr;
System.out.println(arr2[2][1] + arr2[1][2]);
What is the output of the given code snippet on execution?
A) 5
B) 6
C) 7
D) 9

Accepted Answer

The answer of Consider the following code snippet:
Int[][] arr =
{
{...

Question 14

Which statement is true about the code snippet below? Public static void main(String[] args) { Scanner in = new Scanner(System.in); ArrayList inputs = new ArrayList(); Int ind = 0; While (in.hasNextDouble()) { Inputs.set(ind, in.nextDouble()); Ind++; } } A) The code adds all input numbers to the array list B) The code has compile-time error C) The array list is full after 100 numbers are entered D) The code has a run-time error

Accepted Answer

The code has a run-time error because the array list is not initialized with a size, and the set() method is called on an index that is out of bounds.

Question 15

Which one of the following statements is correct for displaying the value in the third row and the fourth column of a two-dimensional 5 by 6 array?
A) System.out.println(arr[2][3]);
B) System.out.println(arr[3][4]);
C) System.out.println(arr[3][2]);
D) System.out.println(arr[4][3]);

Accepted Answer

The answer of Which one of the following statements is...

Question 16

What is the output of the following statements? ArrayList cityList = new ArrayList(); CityList.add("London"); CityList.add("New York"); CityList.add("Paris"); CityList.add("Toronto"); CityList.add("Hong Kong"); CityList.add("Singapore"); System.out.print(cityList.size()); System.out.print(" " + cityList.contains("Toronto")); System.out.print(" " + cityList.indexOf("New York")); System.out.println(" " + cityList.isEmpty()); A) 5 true 1 false B) 6 true 2 false C) 5 false 1 false D) 6 true 1 false

Accepted Answer

The output of cityList.size() will be 6 since 6 elements were added to the list. 
The output of cityList.contains("Toronto") will be true since "Toronto" was added to the list. 
The output of cityList.indexOf("New York") will be 1 since "New York" is the second element added to the list (indexes start at 0). 
The output of cityList.isEmpty() will be false since the list contains elements.

Question 17

What is the output of the following statements? ArrayList names = new ArrayList(); Names.add("Bob"); Names.add(0, "Ann"); Names.remove(1); Names.add("Cal"); Names.set(1, "Tony"); For (String s : names) { System.out.print(s + ", "); } A) Cal, Bob, Ann B) Ann, Bob C) Ann, Tony D) Cal, Bob, Tony

Accepted Answer

The answer of What is the output of the following...

Question 18

Which one of the following is the correct code snippet for calculating the largest value in an integer array list aList? A) int max = 0; For (int count = 1; count < aList.size(); count++) { If (aList.get(count) > max) { Max = aList.get(count); } } B) int max = aList.get(0); For (int count = 1; count < aList.size(); count++) { If (aList.get(count) > max) { Max = aList.get(count); } } C) int max = aList[1]; For (int count = 1; count < aList.size();count++) { If (aList.get(count) > max) { Max = aList.get(count); } } D) int max = aList.get(0); For (int count = 1; count > aList.size();count++) { If (aList.get(count) >= max) { Max = aList.get(count); } }

Accepted Answer

Choice B correctly initializes the max variable with the first element of the list and then iterates through the rest of the list to find the largest element. Choices A, C, and D contain syntax errors or logical errors that would result in incorrect output or a runtime error.

Question 19

Consider the following code snippet. What does the array contain at the end of the program?
Public static fillWithRandomNumbers(double[] values)
{
Double[] numbers = new double[values.length];
For (int i = 0; i < numbers.length; i++)
{
Numbers[i] = Math.random();
}
Values = numbers;
}
Public static void main(String[] args)
{
Double[] num = new double[20];
FillWithRandomNumbers(num);
}
A) 20 random numbers
B) Undefined data due to compilation error
C) 20 zeros because array num is not changed by method
D) Array index bound error

Accepted Answer

The code snippet creates an array of 20 doubles named "num" and passes it to the "fillWithRandomNumbers" method. Inside the method, the code creates a new array named "numbers" of the same length as "values" (which is "num"). Then, it uses a loop to fill "numbers" with random double values. Finally, the method assigns the "numbers" array to the "values" parameter, which is a reference to the "num" array in the main method. Therefore, when the method returns, the "num" array in the main method should contain the same random values as the "numbers" array created inside the method. Thus, the array contains 20 random numbers.

Question 20

What should you check for when calculating the smallest value in an array list?
A) The array list contains at least one element.
B) The array list contains at least two elements.
C) The array list contains the maximum value in the first element.
D) The array list contains the minimum value in the first element.

Accepted Answer

To calculate the smallest value in an array list, it's essential to ensure that the array list contains at least one element. Without any elements, it's impossible to determine a smallest value. The number of elements, whether the maximum or minimum value is in the first element, does not affect the ability to calculate the smallest value as long as there is at least one element to compare.

Quiz 6: Arrays and Arraylists

When an integer literal is added to an array list declared as ArrayList<Integer>, Java performs:

What is the output of the code snippet below? Int[][] arr = { { 1, 2, 3, 0 }, { 4, 5, 6, 0 }, { 0, 0, 0, 0 } }; Int val = arr[1][2] + arr[1][3]; System.out.println(val) ;

Which statement is true about the code snippet below? ArrayList<String> names = new ArrayList<String>() ; Names.add("John") ; Names.add("Jerry") ; ArrayList<String> friends = new ArrayList<String>(names) ; Names.add("Harry") ;

What is the output of the following statements? ArrayList<String> names = new ArrayList<String>() ; Names.add("Bob") ; Names.add(0, "Ann") ; Names.remove(1) ; Names.add("Cal") ; Names.set(2, "Tony") ; For (String s : names) { System.out.print(s + ", ") ; }

Which statement is true about the code snippet below? ArrayList<String> names = new ArrayList<String>() ; Names.add("John") ; Names.add("Jerry") ; ArrayList<String> friends = new ArrayList<String>(names) ; Friends.add("Harry") ;

What is the output of the following code? Int[][] counts = { { 0, 0, 1 }, { 0, 1, 1, 2 }, { 0, 0, 1, 4, 5 }, { 0, 2 } }; System.out.println(counts[3].length) ;

How many elements can be stored in a two-dimensional 5 by 6 array?

What is the output of the code snippet below? Int[][] numarray = { { 8, 7, 6 }, { 0, 0, 0 } }; System.out.print(numarray[0][0]) ; System.out.print(numarray[1][0]) ;

Which statement is true about the code snippet below? ArrayList<String> names = new ArrayList<String>() ; Names.add("John") ; Names.add("Jerry") ; ArrayList<String> friends = names; Friends.add("Harry") ;

Consider the following code snippet: Int[][] arr = { { 1, 2, 3, 0 }, { 4, 5, 6, 0 }, { 0, 0, 0, 0 } }; Int[][] arr2 = arr; System.out.println(arr2[2][1] + arr2[1][2]) ; What is the output of the given code snippet on execution?

Which statement is true about the code snippet below? Public static void main(String[] args) { Scanner in = new Scanner(System.in) ; ArrayList<Double> inputs = new ArrayList<Double>() ; Int ind = 0; While (in.hasNextDouble() ) { Inputs.set(ind, in.nextDouble() ) ; Ind++; } }

Which one of the following statements is correct for displaying the value in the third row and the fourth column of a two-dimensional 5 by 6 array?

What is the output of the following statements? ArrayList<String> names = new ArrayList<String>() ; Names.add("Bob") ; Names.add(0, "Ann") ; Names.remove(1) ; Names.add("Cal") ; Names.set(1, "Tony") ; For (String s : names) { System.out.print(s + ", ") ; }

Which one of the following is the correct code snippet for calculating the largest value in an integer array list aList?

What should you check for when calculating the smallest value in an array list?