# Java quiz 20 MCQS

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Question 1 (5 points)

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Method A invokes method A itself. This is called _________.

Question 1 options:

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indirect recursion

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explicit recursion

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direct recursion

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one-step recursion

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Question 2 (5 points)

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What are the base cases in the following recursive method?

public static void recurse(int n)

{

if (n > 0)

{

System.out.print(n % 10);

recurse(n / 10);

}

}

Question 2 options:

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n < 0

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n <= 0

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n > 0

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no base cases

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Question 3 (5 points)

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What will be displayed by the method call recurse(1234)?

public static void recurse(int n)

{

if (n <= 0)

{

System.out.print(n % 10);

recurse(n / 10);

}

}

Question 3 options:

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1234

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4 3 2 1

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Nothing

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4321

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Question 4 (5 points)

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Analyze the following recursive method and indicate which of the following will be true.

public static long factorial(int n)

{

return n * factorial(n – 1);

}

Question 4 options:

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Invoking factorial(2) returns 2.

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Invoking factorial(1) returns 1.

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The method runs infinitely and causes a StackOverflowError.

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Invoking factorial(0) returns 0.

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Question 5 (5 points)

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Fill in the code to complete the following method for computing factorial.

// Return the factorial for a specified index

public static long factorial(int n)

{

if (n == 0)

return 1;

else

return _____________;

}

Question 5 options:

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n * (n – 1)

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n

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n * factorial(n – 1)

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factorial(n – 1) * (n – 1)

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Question 6 (5 points)

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What will be displayed by the method call recurse(6)?

public static intrecurse(int n)

{

if (n <= 1)

return 1;

else

return n + recurse(n – 2);

}

Question 6 options:

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13

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14

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11

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12

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Question 7 (5 points)

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The base case _________ the recursion.

Question 7 options:

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stops

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breaks

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pauses

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starts

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Question 8 (5 points)

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What is the output of the following program?

{

public static void main(String[] args)

{

System.out.println(countDown(2, 0));

}

public static intcountDown(int n, int result)

{

if (n == 0)

return 0;

else

return countDown(n – 1, n + result);

}

}

Question 8 options:

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1

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3

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0

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2

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Question 9 (5 points)

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Which of the following statements about recursive methods is accurate?

Question 9 options:

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They must have exactly 1 base case and exactly 1 recursive case

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They must have at least 1 base case and at least 1 recursive case

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They must have exactly 1 base case and at least 1 recursive case

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They must have at least 1 base case and exactly 1 recursive case

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Question 10 (5 points)

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Which of the following is a possible disadvantage of recursion?

Question 10 options:

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Recursive solutions can be less efficient than their iterative counterparts

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Recursive solutions tend to have more local variables than their iterative counterparts

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Recursive solutions tend to be longer than their iterative counterparts

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Recursive solutions are more likely to go into infinite loops than their iterative counterparts

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Question 11 (5 points)

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To declare an interface named A with two generic types, use

Question 11 options:

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public interface A(E) { … }

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public interface A<E, F> { … }

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public interface A<E> { … }

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public interface A(E, F) { … }

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Question 12 (5 points)

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Will the following code have a runtime error?

Comparable date = new Date();

inti = date.compareTo(“time”);

Question 12 options:

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Always

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Never

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Only when date contains an invalid date

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Only when date is not the current date

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Question 13 (5 points)

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To create a list to store integers, use

Question 13 options:

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ArrayList<Object> list = new ArrayList<Integer>();

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ArrayList<Number> list = new ArrayList<Integer>();

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ArrayList<int> list = new ArrayList();

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ArrayList<Integer> list = new ArrayList();

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Question 14 (5 points)

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To create a generic type bounded by Number, use

Question 14 options:

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<E extends Object>

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<E extends Number>

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<E>

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<E extends Integer>

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Question 15 (5 points)

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Which of the following describes the benefit of using generic classes to implement collections?

Question 15 options:

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It eliminates the need to downcast objects when they are removed from a collection

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It eliminates the need to upcast objects when they are inserted into a collection

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It eliminates the need to downcast objects when they are inserted into a collection

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It eliminates the need to upcast objects when they are removed from a collection

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Question 16 (5 points)

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Suppose list list1 is [1, 2, 5] and list list2 is [2, 3, 6]. After list1.addAll(list2), list2 is __________.

Question 16 options:

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[1, 5]

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[1, 2, 3, 5, 6]

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[2, 3, 6]

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[1, 2, 2, 3, 5, 6]

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Question 17 (5 points)

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Suppose a list contains {red, red, red, red}. What is the list after the following code?

String element = “red”;

for (inti = list.size() – 1; i>= 0; i–)

if (list.get(i).equals(element))

list.remove(element);

Question 17 options:

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[red]

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[red, red]

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[]

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[red, red, red]

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Question 18 (5 points)

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Which of the following is correct to sort the elements in a list aList?

Question 18 options:

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Arrays.sort(aList)

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new LinkedList<String>(new String[]{red, green, blue})

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Collections.sort(aList)

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aList.sort()

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Question 19 (5 points)

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Which of the following best describes all objects of type List?

Question 19 options:

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They define an ordered collection that prohibits duplicates

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They define an ordered collection that allows duplicates

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They define an unordered collection that allows duplicates

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They define an unordered collection that prohibits duplicates

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Question 20 (5 points)

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Which of the following problems would be a good candidate for using a stack?

Question 20 options:

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A print spooler that dispatches jobs based on shortest job first

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An inventory system that processes product records by product number

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A program that is designed to evaluate expressions

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A task scheduler that schedules tasks in the order that they are received

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