+ * + * The process of implementing a set by extending this class is identical + * to that of implementing a Collection by extending AbstractCollection, + * except that all of the methods and constructors in subclasses of this + * class must obey the additional constraints imposed by the Set + * interface (for instance, the add method must not permit addition of + * multiple instances of an object to a set).
+ * + * Note that this class does not override any of the implementations from + * the AbstractCollection class. It merely adds implementations + * for equals and hashCode.
+ *
+ * This class is a member of the
+ *
+ * Java Collections Framework.
+ *
+ * @param
+ *
+ * This implementation first checks if the specified object is this
+ * set; if so it returns true. Then, it checks if the
+ * specified object is a set whose size is identical to the size of
+ * this set; if not, it returns false. If so, it returns
+ * containsAll((Collection) o).
+ *
+ * @param o object to be compared for equality with this set
+ * @return true if the specified object is equal to this set
+ */
+ public boolean equals(Object o) {
+ if (o == this)
+ return true;
+
+ if (!(o instanceof Set))
+ return false;
+ Collection c = (Collection) o;
+ if (c.size() != size())
+ return false;
+ try {
+ return containsAll(c);
+ } catch (ClassCastException unused) {
+ return false;
+ } catch (NullPointerException unused) {
+ return false;
+ }
+ }
+
+ /**
+ * Returns the hash code value for this set. The hash code of a set is
+ * defined to be the sum of the hash codes of the elements in the set,
+ * where the hash code of a null element is defined to be zero.
+ * This ensures that s1.equals(s2) implies that
+ * s1.hashCode()==s2.hashCode() for any two sets s1
+ * and s2, as required by the general contract of
+ * {@link Object#hashCode}.
+ *
+ * This implementation iterates over the set, calling the
+ * hashCode method on each element in the set, and adding up
+ * the results.
+ *
+ * @return the hash code value for this set
+ * @see Object#equals(Object)
+ * @see Set#equals(Object)
+ */
+ public int hashCode() {
+ int h = 0;
+ Iterator This implementation determines which is the smaller of this set
+ * and the specified collection, by invoking the size
+ * method on each. If this set has fewer elements, then the
+ * implementation iterates over this set, checking each element
+ * returned by the iterator in turn to see if it is contained in
+ * the specified collection. If it is so contained, it is removed
+ * from this set with the iterator's remove method. If
+ * the specified collection has fewer elements, then the
+ * implementation iterates over the specified collection, removing
+ * from this set each element returned by the iterator, using this
+ * set's remove method.
+ *
+ * Note that this implementation will throw an
+ * UnsupportedOperationException if the iterator returned by the
+ * iterator method does not implement the remove method.
+ *
+ * @param c collection containing elements to be removed from this set
+ * @return true if this set changed as a result of the call
+ * @throws UnsupportedOperationException if the removeAll operation
+ * is not supported by this set
+ * @throws ClassCastException if the class of an element of this set
+ * is incompatible with the specified collection
+ * (optional)
+ * @throws NullPointerException if this set contains a null element and the
+ * specified collection does not permit null elements
+ * (optional),
+ * or if the specified collection is null
+ * @see #remove(Object)
+ * @see #contains(Object)
+ */
+ public boolean removeAll(Collection c) {
+ boolean modified = false;
+
+ if (size() > c.size()) {
+ for (Iterator i = c.iterator(); i.hasNext(); )
+ modified |= remove(i.next());
+ } else {
+ for (Iterator i = iterator(); i.hasNext(); ) {
+ if (c.contains(i.next())) {
+ i.remove();
+ modified = true;
+ }
+ }
+ }
+ return modified;
+ }
+
+}