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Question 1 Given the interface BagInterface below: /** An interface that describes the operations of a bag of objects. */ public interface BagInterface { /** Gets the current number of entries in this bag. @return the integer number of entries currently in the bag */ public int getCurrentSize(); /** Sees whether this bag is full. @return true if the bag is full, or false if not */ public boolean isFull(); /** Sees whether this bag is empty. @return true if the bag is empty, or false if not */ public boolean isEmpty(); /** Adds a new entry to this bag. @param newEntry the object to be added as a new entry @return true if the addition is successful, or false if not */ public boolean add(T newEntry); /** Removes one unspecified entry from this bag, if possible. @return either the removed entry, if the removal was successful, or null */ public T remove(); /** Removes one occurrence of a given entry from this bag. @param anEntry the entry to be removed @return true if the removal was successful, or false if not */ public boolean remove(T anEntry); /** Removes all entries from this bag. */ public void clear(); /** Counts the number of times a given entry appears in this bag. @param anEntry the entry to be counted @return the number of times anEntry appears in the bag */ public int getFrequencyOf(T anEntry); /** Tests whether this bag contains a given entry. @param anEntry the entry to locate @return true if this bag contains anEntry, or false otherwise */ public boolean contains(T anEntry); /** Retrieves all entries that are in this bag. @return a newly allocated array of all the entries in the bag */ public T[] toArray(); } // end BagInterface Write an ArrayBag class that implement the BagInterface, as shown in the UML diagram below. Set the DEFAULT_CAPACITY to 25. WIA1002/WIB1002 Sem. 2, 2017/2018 Page 2 Question 2 The union of two collections consists of their contents combined into a new collection. Add a method union to the interface BagInterface for the ADT bag that returns as a new bag the union of the bag receiving the call to the method and the bag that is the method’s one argument. Include sufficient comments to fully specify the method. Note that the union of two bags might contain duplicate items. For example, if object x occurs five times in one bag and twice in another, the union of these bags contains x seven times. Specifically, suppose that bag1 and bag2 are Bag objects, where Bag implements BagInterface; bag1 contains the String objects a, b, and c; and bag2 contains the String objects b, b, d, and e. After the statement BagInterface everything = bag1.union(bag2); executes, the bag everything contains the strings a, b, b, b, c, d, and e. Note that union does not affect the contents of bag1 and bag2. Implement the union method in ArrayBag class. WIA1002/WIB1002 Sem. 2, 2017/2018 Page 3 Question 3 The intersection of two collections is a new collection of the entries that occur in both collections. That is, it contains the overlapping entries. Add a method intersection to the interface BagInterface for the ADT bag that returns as a new bag the intersection of the bag receiving the call to the method and the bag that is the method’s one argument. Include sufficient comments to fully specify the method. Note that the intersection of two bags might contain duplicate items. For example, if object x occurs five times in one bag and twice in another, the intersection of these bags contains x twice. Specifically, suppose that bag1 and bag2 are Bag objects, where Bag implements BagInterface; bag1 contains the String objects a, b, and c; and bag2 contains the String objects b, b, d, and e. After the statement BagInterface commonItems = bag1.intersection(bag2); executes, the bag commonItems contains only the string b. If b had occurred in bag1 twice, commonItems would have contained two occurrences of b, since bag2 also contains two occurrences of b. Note that intersection does not affect the contents of bag1 and bag2. Implement the intersection method in ArrayBag class. Question 4 The difference of two collections is a new collection of the entries that would be left in one collection after removing those that also occur in the second. Add a method difference to the interface BagInterface for the ADT bag that returns as a new bag the difference of the bag receiving the call to the method and the bag that is the method’s one argument. Include sufficient comments to fully specify the method. Note that the difference of two bags might contain duplicate items. For example, if object x occurs five times in one bag and twice in another, the difference of these bags contains x three times. Specifically, suppose that bag1 and bag2 are Bag objects, where Bag implements BagInterface; bag1 contains the String objects a, b, and c; and bag2 contains the String objects b, b, d, and e. After the statement BagInterface leftOver1 = bag1.difference(bag2); executes, the bag leftOver1 contains the strings a and c. After the statement BagInterface leftOver2 = bag2.difference(bag1); executes, the bag leftOver2 contains the strings b, d, and e. Note that difference does not affect the contents of bag1 and bag2. Implement the difference method in ArrayBag class. WIA1002/WIB1002 Sem. 2, 2017/2018 Page 4 Question 5 Write a test program ArrayBagDemo.java to test the core methods add, getCurrentSize() and toArray of the class ArrayBag, and the three methods that you implemented in Question 2 to 4 (i.e. union, intersection and difference). Initially the main method creates an empty bag by using the default constructor. Since the capacity of the bag is 25, the array should not get full if you add fewer than 25 entries to it. Thus, add should return true after each of these conditions. The test program’s descriptive output will indicates that the tested methods are correct. In your program: a) Create a private static method named testAdd to test the method Add of ArrayBag: private static void testAdd(BagInterface aBag, String[] content) b) Create a private static method named displayBag to test the methods getCurrentSize() and toArray of ArrayBag while displaying the all the entries of the bag. private static void displayBag(BagInterface aBag) c) The main method: Create two (2) empty ArrayBag objects of the type array for a list of strings, named bag1 and bag2. Then filling an initially empty bag, bag1 ad bag2 with a list of strings using the method testAdd String[] contentsOfBag1 = {“A”, “A”, “B”, “A”, “C”, “A”}; String[] contentsOfBag2 = {“A”, “B”, “A”, “C”, “B”, “C”, “D”, “another string”}; Display the contents of bag1 and bag2 using method displayBag Test the method union using a new bag named bag3 that combines the contents of bag1 and bag2. Display the contents of bag3 using method displayBag. Test the method intersection using a new bag named bag4 that contains those objects that occur in both bag1 and bag2. Display the contents of bag4 using method displayBag. Test the method difference using a new bag named bag5 that create a new bag of objects that would be left in bag1 after removing those that also occur in bag2. Display the contents of bag5 using method displayBag. WIA1002/WIB1002 Sem. 2, 2017/2018 Page 5 An example of the output for the test program is as follows: bag1: Adding A A B A C A The bag contains 6 string(s), as follows: A A B A C A bag2: Adding A B A C B C D another string The bag contains 8 string(s), as follows: A B A C B C D another string bag3, test the method union of bag1 and bag2: The bag contains 14 string(s), as follows: A A B A C A A B A C B C D another string bag4, test the method intersection of bag1 and bag2: The bag contains 4 string(s), as follows: A A B C bag5, test the method difference of bag1 and bag2: The bag contains 2 string(s), as follows: A A
