The following files will be provided to you. BagArray, BagInterface, BagDemo. 1. Test the implementation and produce the output as shown in class 2. Test at least one Add method and one Remove method. 3. Display the bag

/** A class of bags whose entries are stored in a fixed-size array. @author Frank M. Carrano @author Timothy M. Henry @version 4.0 */ public final class ArrayBag implements BagInterface { private final T[] bag; private int numberOfEntries; private boolean initialized = false; private static final int DEFAULT_CAPACITY = 25; private static final int MAX_CAPACITY = 10000;

/** Creates an empty bag whose initial capacity is 25. */ public ArrayBag() { this(DEFAULT_CAPACITY); } // end default constructor

/** Creates an empty bag having a given capacity. @param desiredCapacity The integer capacity desired. */ public ArrayBag(int desiredCapacity) { if (desiredCapacity <= MAX_CAPACITY) { // The cast is safe because the new array contains null entries @SuppressWarnings("unchecked") T[] tempBag = (T[])new Object[desiredCapacity]; // Unchecked cast bag = tempBag; numberOfEntries = 0; initialized = true; } else throw new IllegalStateException("Attempt to create a bag " + "whose capacity exceeds " + "allowed maximum."); } // end constructor /** 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) { checkInitialization(); boolean result = true; if (isArrayFull()) { result = false; } else { // Assertion: result is true here bag[numberOfEntries] = newEntry; numberOfEntries++; } // end if return result; } // end add /** Retrieves all entries that are in this bag. @return A newly allocated array of all the entries in this bag. */ public T[] toArray() { checkInitialization(); // The cast is safe because the new array contains null entries. @SuppressWarnings("unchecked") T[] result = (T[])new Object[numberOfEntries]; // Unchecked cast

for (int index = 0; index < numberOfEntries; index++) { result[index] = bag[index]; } // end for return result; // Note: The body of this method could consist of one return statement, // if you call Arrays.copyOf } // end toArray

/** Sees whether this bag is empty. @return True if this bag is empty, or false if not. */ public boolean isEmpty() { return numberOfEntries == 0; } // end isEmpty

/** Gets the current number of entries in this bag. @return The integer number of entries currently in this bag. */ public int getCurrentSize() { return numberOfEntries; } // end getCurrentSize

/** 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 this ba. */ public int getFrequencyOf(T anEntry) { checkInitialization(); int counter = 0;

for (int index = 0; index < numberOfEntries; index++) { if (anEntry.equals(bag[index])) { counter++; } // end if } // end for

return counter; } // end getFrequencyOf

/** 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) { checkInitialization(); return getIndexOf(anEntry) > -1; // or >= 0 } // end contains /** Removes all entries from this bag. */ public void clear() { while (!isEmpty()) remove(); } // end clear /** Removes one unspecified entry from this bag, if possible. @return Either the removed entry, if the removal was successful, or null. */ public T remove() { checkInitialization(); T result = removeEntry(numberOfEntries - 1); return result; } // end 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) { checkInitialization(); int index = getIndexOf(anEntry); T result = removeEntry(index); return anEntry.equals(result); } // end remove // Returns true if the array bag is full, or false if not. private boolean isArrayFull() { return numberOfEntries >= bag.length; } // end isArrayFull // Locates a given entry within the array bag. // Returns the index of the entry, if located, // or -1 otherwise. // Precondition: checkInitialization has been called. private int getIndexOf(T anEntry) { int where = -1; boolean found = false; int index = 0; while (!found && (index < numberOfEntries)) { if (anEntry.equals(bag[index])) { found = true; where = index; } // end if index++; } // end while // Assertion: If where > -1, anEntry is in the array bag, and it // equals bag[where]; otherwise, anEntry is not in the array. return where; } // end getIndexOf // Removes and returns the entry at a given index within the array. // If no such entry exists, returns null. // Precondition: 0 <= givenIndex < numberOfEntries. // Precondition: checkInitialization has been called. private T removeEntry(int givenIndex) { T result = null; if (!isEmpty() && (givenIndex >= 0)) { result = bag[givenIndex]; // Entry to remove int lastIndex = numberOfEntries - 1; bag[givenIndex] = bag[lastIndex]; // Replace entry to remove with last entry bag[lastIndex] = null; // Remove reference to last entry numberOfEntries--; } // end if return result; } // end removeEntry // Throws an exception if this object is not initialized. private void checkInitialization() { if (!initialized) throw new SecurityException("ArrayBag object is not initialized properly."); } // end checkInitialization } // end ArrayBag

/** A demonstration of the class ArrayBag @author Frank M. Carrano @author Timothy M. Henry @version 4.0 */ public class ArrayBagDemo { public static void main(String[] args) { String[] contentsOfBag = {"A", "A", "B", "A", "C", "A"};

// Tests on an empty bag BagInterface aBag = new ArrayBag<>(contentsOfBag.length); System.out.println("Testing an initially empty bag:"); testIsEmpty(aBag, true); String[] testStrings1 = {"", "B"}; testFrequency(aBag, testStrings1); testContains(aBag, testStrings1); testRemove(aBag, testStrings1);

// Adding strings System.out.println("Adding " + contentsOfBag.length + " strings to an initially empty bag with" + " the capacity to hold more than " + contentsOfBag.length + " strings:"); testAdd(aBag, contentsOfBag); // Tests on a bag that is not empty testIsEmpty(aBag, false); String[] testStrings2 = {"A", "B", "C", "D", "Z"}; testFrequency(aBag, testStrings2); testContains(aBag, testStrings2); // Removing strings String[] testStrings3 = {"", "B", "A", "C", "Z"}; testRemove(aBag, testStrings3);

System.out.println(" Clearing the bag:"); aBag.clear(); testIsEmpty(aBag, true); displayBag(aBag); // Filling an initially empty bag to capacity System.out.println(" Testing an initially empty bag that " + " will be filled to capacity:"); aBag = new ArrayBag(7); String[] contentsOfBag2 = {"A", "B", "A", "C", "B", "C", "D"}; testAdd(aBag, contentsOfBag2); System.out.println("Try to add another string to the full bag:"); if (aBag.add("another string")) System.out.println("Added a string beyond the bag's capacity: ERROR!"); else System.out.println("The method add cannot add another string: OK"); } // end main // Tests the method add. private static void testAdd(BagInterface aBag, String[] content) { System.out.print("Adding "); for (int index = 0; index < content.length; index++) { aBag.add(content[index]); System.out.print(content[index] + " "); } // end for System.out.println(); displayBag(aBag); } // end testAdd

// Tests the two remove methods. private static void testRemove(BagInterface aBag, String[] tests) { for (int index = 0; index < tests.length; index++) { String aString = tests[index]; if (aString.equals("") || (aString == null)) { // test remove() System.out.println(" Removing a string from the bag:"); String removedString = aBag.remove(); System.out.println("remove() returns " + removedString); } else { // test remove(aString) System.out.println(" Removing \"" + aString + "\" from the bag:"); boolean result = aBag.remove(aString); System.out.println("remove(\"" + aString + "\") returns " + result); } // end if displayBag(aBag); } // end for } // end testRemove

// Tests the method isEmpty. // correctResult indicates what isEmpty should return. private static void testIsEmpty(BagInterface aBag, boolean correctResult) { System.out.print("Testing isEmpty with "); if (correctResult) System.out.println("an empty bag:"); else System.out.println("a bag that is not empty:"); System.out.print("isEmpty finds the bag "); if (correctResult && aBag.isEmpty()) System.out.println("empty: OK."); else if (correctResult) System.out.println("not empty, but it is empty: ERROR."); else if (!correctResult && aBag.isEmpty()) System.out.println("empty, but it is not empty: ERROR."); else System.out.println("not empty: OK."); System.out.println(); } // end testIsEmpty

// Tests the method getFrequencyOf. private static void testFrequency(BagInterface aBag, String[] tests) { System.out.println(" Testing the method getFrequencyOf:"); for (int index = 0; index < tests.length; index++) { String aString = tests[index]; if (!aString.equals("") && (aString != null)) { System.out.println("In this bag, the count of " + tests[index] + " is " + aBag.getFrequencyOf(tests[index])); } // end if } // end for } // end testFrequency // Tests the method contains. private static void testContains(BagInterface aBag, String[] tests) { System.out.println(" Testing the method contains:"); for (int index = 0; index < tests.length; index++) { String aString = tests[index]; if (!aString.equals("") && (aString != null)) { System.out.println("Does this bag contain " + tests[index] + "? " + aBag.contains(tests[index])); } // end if } // end for } // end testContains

// Tests the method toArray while displaying the bag. private static void displayBag(BagInterface aBag) { System.out.println("The bag contains " + aBag.getCurrentSize() + " string(s), as follows:"); Object[] bagArray = aBag.toArray(); for (int index = 0; index < bagArray.length; index++) { System.out.print(bagArray[index] + " "); } // end for System.out.println(); } // end displayBag } // end ArrayBagDemo

/* Testing an initially empty bag: Testing isEmpty with an empty bag: isEmpty finds the bag empty: OK. Testing the method getFrequencyOf: In this bag, the count of B is 0 Testing the method contains: Does this bag contain B? false Removing a string from the bag: remove() returns null The bag contains 0 string(s), as follows: Removing "B" from the bag: remove("B") returns false The bag contains 0 string(s), as follows: Adding 6 strings to an initially empty bag with the capacity to hold more than 6 strings: Adding A A B A C A The bag contains 6 string(s), as follows: A A B A C A Testing isEmpty with a bag that is not empty: isEmpty finds the bag not empty: OK. Testing the method getFrequencyOf: In this bag, the count of A is 4 In this bag, the count of B is 1 In this bag, the count of C is 1 In this bag, the count of D is 0 In this bag, the count of Z is 0 Testing the method contains: Does this bag contain A? true Does this bag contain B? true Does this bag contain C? true Does this bag contain D? false Does this bag contain Z? false Removing a string from the bag: remove() returns A The bag contains 5 string(s), as follows: A A B A C Removing "B" from the bag: remove("B") returns true The bag contains 4 string(s), as follows: A A C A Removing "A" from the bag: remove("A") returns true The bag contains 3 string(s), as follows: A A C Removing "C" from the bag: remove("C") returns true The bag contains 2 string(s), as follows: A A Removing "Z" from the bag: remove("Z") returns false The bag contains 2 string(s), as follows: A A Clearing the bag: Testing isEmpty with an empty bag: isEmpty finds the bag empty: OK. The bag contains 0 string(s), as follows: Testing an initially empty bag that will be filled to capacity: Adding A B A C B C D The bag contains 7 string(s), as follows: A B A C B C D Try to add another string to the full bag: The method add cannot add another string: OK */

/** LISTING 1-1 An interface that describes the operations of a bag of objects. @author Frank M. Carrano @version 3.0 */ 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();

/** Creates a new bag that combines the contents of this bag and anotherBag. @param anotherBag the bag that is to be added @return a combined bag */ // public BagInterface union(BagInterface anotherBag);

/** Creates a new bag that contains those objects that occur in both this bag and anotherBag. @param anotherBag the bag that is to be compared @return a combined bag */ // public BagInterface intersection(BagInterface anotherBag);

/** Creates a new bag of objects that would be left in this bag after removing those that also occur in anotherBag. @param anotherBag the bag that is to be removed @return a combined bag */ // public BagInterface difference(BagInterface anotherBag); } // end BagInterface