Question 1

To create a set that consists of string elements "red", "green", and "blue", use

Accepted Answer

Option C is the correct choice because it uses the constructor of HashSet that takes a Collection object as an argument. The Arrays.asList method is used to convert the array of strings into a List and provide it as an argument to the constructor. This way, a new HashSet object is created with the elements "red", "green" and "blue". Option A is also correct, but it uses a longer syntax to create a HashSet object. Option B is incorrect because there is no class named Set in Java. Option D is incorrect because curly braces can only be used to create an array in Java, but not for creating a HashSet object.

Question 2

Suppose List list = new ArrayList(). Which of the following operations are correct? A. list.add(new Integer(100)); B) list.add(new ArrayList()); C) list.add("Red"); D) list.add(new java.util.Date());

Accepted Answer

C

Question 3

To create a list to store integers, use B. ArrayList list = new ArrayList(); C) ArrayList

Accepted Answer

A

Question 4

Show the time complexity of the following program:
for (int k = 0; k < 10; k++) {
for (int i = 0; i < n; i++) {
for (int j = 0; j < n; j++) {
System.out.print('*');
}
}
}

Accepted Answer

The answer of Show the time complexity of the following...

Question 5

Write a recursive mathematical definition for computing  for a positive integer.

Accepted Answer

The answer of Write a recursive mathematical definition for computing...

Question 6

(Displaying words) Write a program that reads words separated by spaces from a text file and displays words in ascending order. (If two words are the same, display only one). Pass the text filename from the command line.

Accepted Answer

The answer of (Displaying words) Write a program that reads...

Question 7

Suppose your program frequently tests whether a student is in a soccer team, what is the best data structure to store the students in a soccer team?

Accepted Answer

A HashSet offers constant time performance for the basic operations (add, remove, contains, and size) and can efficiently store a large number of items. Since the program frequently tests whether a student is in a soccer team, performance is an important consideration. Additionally, a HashSet does not allow for duplicate entries, which could be useful in ensuring that the program accurately reflects the composition of the soccer team.

Question 8

Suppose the rule of the party is that the participants who arrive later will leave earlier. Which data structure is appropriate to store the participants?

Accepted Answer

A stack is the most appropriate data structure for this scenario because it follows the Last In, First Out (LIFO) principle, which aligns with the party rule that the participants who arrive later will leave earlier.

Question 9

Are there any compile errors in (a) and (b)?

Accepted Answer

The answer of Are there any compile errors in (a)...

Question 10

Which method do you use to remove an element from a set or list named x?

Accepted Answer

The correct method to remove an element from a set or list is x.remove(element). This method removes the first occurrence of the specified element from the set or list. The other options (B, C, D, and E) are not valid methods for removing an element from a set or list.

Question 11

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

Accepted Answer

The Collections.sort method is used to sort elements in a list. Option A creates a new linked list but does not sort the original list. Option B is not a valid method to sort a list. Option C is used to sort arrays, not lists. Therefore, the correct answer is D, which sorts the elements in the original list using the Collections.sort method.

Question 12

Fill in the code in Comparable______ c = new Date(); A. B) C)

Accepted Answer

The answer of Fill in the code in Comparable______ c...

Question 13

Design an efficient O(logn) time algorithm for computing  . (Describe it using a pseudo code)

Accepted Answer

The answer of Design an efficient O(logn) time algorithm for...

Question 14

Suppose that set1 (Set) is a set that contains the strings "red", "yellow", "green", and that set2 (Set) is another set that contains the strings "red", "yellow", "blue". Answer the following questions: (All the questions are independent) •What are set1 and set2 after executing set1.addAll(set2)? •What are set1 and set2 after executing set1.add(set2)? •What are set1 and set2 after executing set1.removeAll(set2)? •What are set1 and set2 after executing set1.remove(set2)? •What are set1 and set2 after executing set1.retainAll(set2)? •What is set1 after executing set1.clear()?

Accepted Answer

The answer of Suppose that set1 (Set<String>) is a set...

Question 15

Show the output of the following program:

Accepted Answer

The answer of Show the output of the following program:...

Question 16

To find a maximum object in an array of strings (e.g., String[] names = {"red", "green", "blue"}), use

Accepted Answer

Arrays.max() only works with arrays of primitive types or with objects that implement the Comparable interface. String implements Comparable, but Arrays.max() still won't work directly with an array of strings. Collections.max() works with any collection that contains objects that implement Comparable, and Arrays.asList() can be used to turn an array into a List. So, the best choice is B, which uses Collections.max() with Arrays.asList() to find the maximum string in the array.

Question 17

Which of the data types below could be used to store elements in their natural order based on the compareTo method.

Accepted Answer

TreeSet is the only data type listed that maintains elements in their natural order based on the compareTo method. The other options do not guarantee any specific ordering of elements.

Question 18

How many times is the factorial method in Listing 20.1 invoked for factorial(5)?

Accepted Answer

The factorial method is invoked once for the initial call factorial(5), and then it recursively calls itself for factorial(4), factorial(3), factorial(2), and factorial(1), totaling 6 invocations.

Question 19

Show the printout of the following code: Test { main(String[] args) { Map map = LinkedHashMap(); map.put("123", "John Smith"); map.put("111", "George Smith"); map.put("123", "Steve Yao"); map.put("222", "Steve Yao"); System.out.println("(1) " + map); System.out.println("(2) " + new TreeMap(map)); } }

Accepted Answer

The answer of Show the printout of the following code:
Test...

Question 20

To declare an interface named A with two generic types, use A. public interface A(E, F) { ... }
B) public interface A<E> { ... }
D) public interface A(E) { ... }

Accepted Answer

The answer of To declare an interface named A with...

Quiz 3: Selections

To create a set that consists of string elements "red", "green", and "blue", use

Suppose List<String> list = new ArrayList<String>(). Which of the following operations are correct? A. list.add(new Integer(100)); B) list.add(new ArrayList()); C) list.add("Red"); D) list.add(new java.util.Date());

To create a list to store integers, use B. ArrayList<Number> list = new ArrayList<Integer>(); C) ArrayList<Object> list = new ArrayList<Integer>(); D) ArrayList<int> list = new ArrayList<int>();

Show the time complexity of the following program: for (int k = 0; k < 10; k++) { for (int i = 0; i < n; i++) { for (int j = 0; j < n; j++) { System.out.print('*'); } } }

Write a recursive mathematical definition for computing for a positive integer.

(Displaying words) Write a program that reads words separated by spaces from a text file and displays words in ascending order. (If two words are the same, display only one). Pass the text filename from the command line.

Suppose your program frequently tests whether a student is in a soccer team, what is the best data structure to store the students in a soccer team?

Suppose the rule of the party is that the participants who arrive later will leave earlier. Which data structure is appropriate to store the participants?

Are there any compile errors in (a) and (b)?

Which method do you use to remove an element from a set or list named x?

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

Fill in the code in Comparable______ c = new Date(); A. <E> B) <?> C) <String>

Design an efficient O(logn) time algorithm for computing . (Describe it using a pseudo code)

Show the output of the following program:

To find a maximum object in an array of strings (e.g., String[] names = {"red", "green", "blue"}) , use

Which of the data types below could be used to store elements in their natural order based on the compareTo method.

How many times is the factorial method in Listing 20.1 invoked for factorial(5) ?

To declare an interface named A with two generic types, use A. public interface A(E, F) { ... } B) public interface A<E> { ... } D) public interface A(E) { ... }