Exam 15: The Java Collections Framework

Which of the following algorithms would be efficiently executed on an ArrayList?

The ArrayList class implements the ____.

Consider the code snippet shown below. Assume that employeeNames is an instance of type LinkedList<String>. for (String name : employeeNames) { // Do something with name here } Which element(s) of employeeNames does this loop process?

Select an appropriate expression to complete the following code segment, which is designed to print a message if the string stored in name is part of the players collection. Collection<String> players = new ArrayList<String>(); // code to add elements to the collection here If ______________________________________ System.out.print(name + " is one of the players in the collection.");

Assuming that names is a Queue of String objects, select a statement to complete the code segment below. The code is designed to remove the last element from the queue, which is guaranteed to have at least one element. Queue<String> aQueue = new LinkedList<String>(); While (names.size() > 1) { AQueue.add(names.remove()); } Names.remove(); While (aQueue.size() > 0) { ____________________________ }

Rather than storing values in an array, a linked list uses a sequence of ____.

A collection that allows speedy insertion and removal of already-located elements in the middle of it is called a ____.

Select an appropriate expression to complete the following method, which is designed to return the number of elements in the parameter array numbers. If a value appears more than once, it should be counted exactly once. public static int countElementsOnce(int[] numbers) { Set<Integer> values = new HashSet<Integer>(); For (int num: numbers) { Values.add(num); } ______________________ }

Assume that you have declared a map named myMap to hold String elements with Integer keys. Which of the following statements will correctly insert an element into myMap?

Which of the following statements about hash functions is NOT correct?

Complete the following code, which is intended to print out all key/value pairs in a map named myMap that contains String data for student IDs and names: Map<String, String> myMap = new HashMap<String, String>(); ) . . Set<String> mapKeySet = myMap.keySet(); For (String aKey : mapKeySet) { ___________________________; System.out.println("ID: " + aKey + "->" + name); }

When using a list iterator, on which condition will the IllegalStateException be thrown?

Select an appropriate declaration to complete the following code segment, which is designed to read strings from standard input and display them in increasing alphabetical order, excluding any duplicates. _________________________________________ Scanner input = new Scanner(System.in); While (input.hasNext()) { Words.add(input.next()); } System.out.print(words);

What is the meaning of the type parameter E, in the LinkedList<E> code fragment?

You intend to use a hash set with your own object class. Which of the following statements is NOT correct?

Consider the code snippet shown below: Stack<String> words1 = new Stack<String>(); Stack<String> words2 = new Stack<String>(); Words1.push("abc"); Words1.push("def"); Words1.push("ghi"); While (!words1.empty()) { Words2.push(words1.pop()); } While (!words2.empty()) { System.out.print(words2.pop()); } What will be printed when this code is executed?

Assume you have created a linked list name myList that currently holds some number of String objects. Which of the following statements correctly removes an element from the end of myList?

What operation is least efficient in a LinkedList?

Which of the following statements about the LinkedList class is correct?

Which data structure would best be used for finding a path out of a maze?