this file has a complete array-based MultiSet, but not the code need.pdf

this file has a complete array-based MultiSet, but not the code need.pdf

• 1.
  this file hasa complete array-based MultiSet, but not the code needed to support its Iterator. Complete the Iterator's next() and hasNext() methods. Solution Hi, I have implemented required methods. Please let me know in case of any issue. import java.util.Collection; import java.util.Iterator; import java.util.NoSuchElementException; public class ArrayMultiSet implements Collection { /** Array in which the elements in this multiset are stored. */ private E[] _store; /** * Array indices below this amount contain the active elements in this collection. */ private int _size; /** * Modification counter used to preserve the fail-fast nature of its iterators. */ private long _modCount; /** * Create a new empty multiset. */ public ArrayMultiSet() { _modCount = 0; clear(); } /** * Remove all of the elements within the instance and invalidate any current iterators. */ @SuppressWarnings("unchecked") @Override public void clear() { _store = (E[]) (new Object[16]);
• 2.
  _size = 0; //maintains the class invariant } /** * Update the multiset so that it includes all of the elements from before the call AND the given element. * * @param e Item to be added to this collection. */ @SuppressWarnings("unchecked") @Override public boolean add(E e) { // Check if we do not have enough space in the underlying array to store the // new element if (_size == _store.length) { // We do not have space, so create a new larger space (doubling the size // is the most time efficient) E[] newStore = (E[]) new Object[_store.length * 2]; // Copy all of the references into the new array for (int i = 0; i < _store.length; i++ ) { newStore[i] = _store[i]; } _store = newStore; // An easier, more efficient way of coding this (but less useful for // teaching) would instead be: // _store = Arrays.copyOf(_store, _store.length * 2); } // Add the element to the store _store[_size] = e; // Finally, we can increase _size, since this change will no longer violate // any class invariants. _size += 1; return true; } /** * Return true if at least one element in the multiset is equal to the given object. When {@code
• 3.
  obj} is null,it must * use the {@code ==} operator to perform these checks, but when {@code obj} is not null, the {@link Object#equals} * method is used. * * @param obj Object (or null) for which we will search * @return {@code true} if {@code obj} was found; {@code false} if a match could not be found. */ @Override public boolean contains(Object obj) { // Only scan through _size, since those are the only "real" entries for the // multiset. for (int i = 0; i < _size; i++ ) { // When obj is null, we need to use == if ((obj == null) && (_store[i] == null)) { return true; } // Otherwise, we use .equals() to find a match else if ((obj != null) && obj.equals(_store[i])) { return true; } // No else clause, since the match could be at a higher index! } // Checked all VALID indices, so the result must be: return false; } @Override public int size() { return _size; } /** * Remove the element found at the given index. This method also acts to maintain the class invariants. * Precondition: {@code i} is a valid index within {@code _store}.
• 4.
  * * @param iIndex of the element to remove from the multibag. */ private void removeAtIndex(int i) { // We do not need to check i, since we made that a precondition (assumption) // for this method. // Use the last element in the backing store to fill the hole made by the removal. _store[i] = _store[_size - 1]; // Set that last value to null (this is not necessary, but can help optimize performance) _store[_size - 1] = null; // Finally, decrease the value of size _size -= 1; } /** * Removes a single instance of the given object, if one can be found in the multibag. The method returns {@code true} * if a match was found (and removed) and {@code false} if no match was found. Normally, this uses * {@link Object#equals} to check if there is a match, but uses {@code ==} when {@code obj} is {@code null}. * * @param obj Object (or null) which we want to remove * @return {@code true} if {@code obj} was found and an instance removed; {@code false} if a match could not be found. */ @Override public boolean remove(Object obj) { for (int i = 0; i < _size; i++ ) { if ((obj == null) && (_store[i] == null)) { removeAtIndex(i); return true; } else if ((obj != null) && obj.equals(_store[i])) { removeAtIndex(i); return true; } // No else clause, since a match may still exist at a higher index!
• 5.
  } // Checked allVALID indices, so the result must be: return false; } @Override public boolean isEmpty() { return _size == 0; } @Override public Iterator iterator() { return new MultiSetIterator(); } /** * Instances of this class are used as the iterators for a multiset. We must keep this as an inner- class, because the * multiset definition does not include any methods to access its elements. * * @author Carl Alphonce * @author Matthew Hertz */ private class MultiSetIterator implements Iterator { /** * The index of the _store entry which will be returned by the next call to next() */ private int _cursor; /** * In keeping with the fail-fast convention, the iterator is only valid while _modCount remains on this version. */ private long _collectionVersion; /** * Create a new instance of this class that will go through the (valid) entries in the store. */ public MultiSetIterator() { _cursor = 0; _collectionVersion = _modCount;
• 6.
  } public boolean hasNext(){ return _cursor < _size; } public E next() { if(hasNext()) return _store[_cursor++]; else throw new NoSuchElementException(); } public void remove() { throw new UnsupportedOperationException(); } } /* * The remaining methods are part of the Collection interface, but are beyond what is necessary for CSE 116. * Students who want a complete Multiset implementation should investigate Google's "Guava" library. */ @Override public Object[] toArray() { // TODO Auto-generated method stub return null; } @Override public T[] toArray(T[] a) { // TODO Auto-generated method stub return null; } @Override public boolean containsAll(Collection c) { // TODO Auto-generated method stub return false; } @Override
• 7.
  public boolean addAll(Collectionc) { // TODO Auto-generated method stub return false; } @Override public boolean removeAll(Collection c) { // TODO Auto-generated method stub return false; } @Override public boolean retainAll(Collection c) { // TODO Auto-generated method stub return false; } }