Class SingletonSet

lib/java/util/Collections.java:237–279

    }

    private static final class SingletonSet<E> extends AbstractSet<E> implements
            Serializable {
        private static final long serialVersionUID = 3193687207550431679L;

        final E element;

        SingletonSet(E object) {
            element = object;
        }

        @Override
        public boolean contains(Object object) {
            return element == null ? object == null : element.equals(object);
        }

        @Override
        public int size() {
            return 1;
        }

        @Override
        public Iterator<E> iterator() {
            return new Iterator<E>() {
                boolean hasNext = true;

                public boolean hasNext() {
                    return hasNext;
                }

                public E next() {
                    if (hasNext) {
                        hasNext = false;
                        return element;
                    }
                    throw new NoSuchElementException();
                }

                public void remove() {
                    throw new UnsupportedOperationException();
                }
            };
        }
    }

    private static final class SingletonList<E> extends AbstractList<E>
            implements Serializable {