/**
* Returns <tt>true</tt> if this collection contains the specified element. More formally, returns
* <tt>true</tt> if and only if this collection contains at least one element <tt>e</tt> such that
* <tt>(o==null ? e==null : o.equals(e))</tt>.
*
* <p>This implementation iterates over the elements in the collection, checking each element in
* turn for equality with the specified element.
*
* @param o object to be checked for containment in this collection.
* @return <tt>true</tt> if this collection contains the specified element.
*/
public boolean contains(Object o) {
Iterator<T> e = iterator();
if (o == null) {
while (e.hasNext()) if (e.next() == null) return true;
} else {
while (e.hasNext()) if (o.equals(e.next())) return true;
}
return false;
}
/**
* Removes from this collection all of its elements that are contained in the specified collection
* (optional operation).
*
* <p>This implementation iterates over this collection, checking each element returned by the
* iterator in turn to see if it's contained in the specified collection. If it's so contained,
* it's removed from this collection with the iterator's <tt>remove</tt> method.
*
* <p>Note that this implementation will throw an <tt>UnsupportedOperationException</tt> if the
* iterator returned by the <tt>iterator</tt> method does not implement the <tt>remove</tt> method
* and this collection contains one or more elements in common with the specified collection.
*
* @param c elements to be removed from this collection.
* @return <tt>true</tt> if this collection changed as a result of the call.
* @throws UnsupportedOperationException if the <tt>removeAll</tt> method is not supported by this
* collection.
* @throws NullPointerException if the specified collection is null.
* @see #remove(Object)
* @see #contains(Object)
*/
public boolean removeAll(Collection<?> c) {
boolean modified = false;
Iterator<?> i = c.iterator();
while (i.hasNext()) {
modified |= remove(i.next());
}
return modified;
}
/**
* Adds all of the elements in the specified collection to this collection (optional operation).
* The behavior of this operation is undefined if the specified collection is modified while the
* operation is in progress. (This implies that the behavior of this call is undefined if the
* specified collection is this collection, and this collection is nonempty.)
*
* <p>This implementation iterates over the specified collection, and adds each object returned by
* the iterator to this collection, in turn.
*
* <p>Note that this implementation will throw an <tt>UnsupportedOperationException</tt> unless
* <tt>add</tt> is overridden (assuming the specified collection is non-empty).
*
* @param c collection whose elements are to be added to this collection.
* @return <tt>true</tt> if this collection changed as a result of the call.
* @throws UnsupportedOperationException if this collection does not support the <tt>addAll</tt>
* method.
* @throws NullPointerException if the specified collection is null.
* @see #add(Object)
*/
public boolean addAll(Collection<? extends T> c) {
boolean modified = false;
Iterator<? extends T> e = c.iterator();
while (e.hasNext()) {
if (add(e.next())) modified = true;
}
return modified;
}
/**
* Removes a single instance of the specified element from this collection, if it is present
* (optional operation). More formally, removes an element <tt>e</tt> such that <tt>(o==null ?
* e==null : o.equals(e))</tt>, if the collection contains one or more such elements. Returns
* <tt>true</tt> if the collection contained the specified element (or equivalently, if the
* collection changed as a result of the call).
*
* <p>This implementation iterates over the collection looking for the specified element. If it
* finds the element, it removes the element from the collection using the iterator's remove
* method.
*
* <p>Note that this implementation throws an <tt>UnsupportedOperationException</tt> if the
* iterator returned by this collection's iterator method does not implement the <tt>remove</tt>
* method and this collection contains the specified object.
*
* @param o element to be removed from this collection, if present.
* @return <tt>true</tt> if the collection contained the specified element.
* @throws UnsupportedOperationException if the <tt>remove</tt> method is not supported by this
* collection.
*/
public boolean remove(Object o) {
Iterator<T> e = iterator();
if (o == null) {
while (e.hasNext()) {
if (e.next() == null) {
e.remove();
return true;
}
}
} else {
while (e.hasNext()) {
if (o.equals(e.next())) {
e.remove();
return true;
}
}
}
return false;
}
/**
* Retains only the elements in this collection that are contained in the specified collection
* (optional operation). In other words, removes from this collection all of its elements that are
* not contained in the specified collection.
*
* <p>This implementation iterates over this collection, checking each element returned by the
* iterator in turn to see if it's contained in the specified collection. If it's not so
* contained, it's removed from this collection with the iterator's <tt>remove</tt> method.
*
* <p>Note that this implementation will throw an <tt>UnsupportedOperationException</tt> if the
* iterator returned by the <tt>iterator</tt> method does not implement the <tt>remove</tt> method
* and this collection contains one or more elements not present in the specified collection.
*
* @param c elements to be retained in this collection.
* @return <tt>true</tt> if this collection changed as a result of the call.
* @throws UnsupportedOperationException if the <tt>retainAll</tt> method is not supported by this
* Collection.
* @throws NullPointerException if the specified collection is null.
* @see #remove(Object)
* @see #contains(Object)
*/
public boolean retainAll(Collection<?> c) {
ArrayList<T> toBeRemoved = new ArrayList<T>();
Iterator<T> i = iterator();
while (i.hasNext()) {
T o = i.next();
if (!c.contains(o)) {
toBeRemoved.add(o);
}
}
int n = toBeRemoved.size();
for (int j = 0; j < n; j++) {
remove(toBeRemoved.get(j));
}
return n != 0;
}
/**
* Returns <tt>true</tt> if this collection contains all of the elements in the specified
* collection.
*
* <p>This implementation iterates over the specified collection, checking each element returned
* by the iterator in turn to see if it's contained in this collection. If all elements are so
* contained <tt>true</tt> is returned, otherwise <tt>false</tt>.
*
* @param c collection to be checked for containment in this collection.
* @return <tt>true</tt> if this collection contains all of the elements in the specified
* collection.
* @throws NullPointerException if the specified collection is null.
* @see #contains(Object)
*/
public boolean containsAll(Collection<?> c) {
Iterator<?> e = c.iterator();
while (e.hasNext()) if (!contains(e.next())) return false;
return true;
}