Collection接口

public interface Collection<E> extends Iterable<E> {
    // Query Operations
    int size();

    boolean isEmpty();
  
    boolean contains(Object o);

    Iterator<E> iterator();
   
    Object[] toArray();
 
    <T> T[] toArray(T[] a);

    boolean remove(Object o);

    boolean containsAll(Collection<?> c);

    boolean addAll(Collection<? extends E> c);

    boolean removeAll(Collection<?> c);

   
    default boolean removeIf(Predicate<? super E> filter) {
        Objects.requireNonNull(filter);
        boolean removed = false;
        final Iterator<E> each = iterator();
        while (each.hasNext()) {
            if (filter.test(each.next())) {
                each.remove();
                removed = true;
            }
        }
        return removed;
    }

    boolean retainAll(Collection<?> c);

    void clear();

    boolean equals(Object o);

    int hashCode();

    @Override
    default Spliterator<E> spliterator() {
        return Spliterators.spliterator(this, 0);
    }

    default Stream<E> stream() {
        return StreamSupport.stream(spliterator(), false);
    }


    default Stream<E> parallelStream() {
        return StreamSupport.stream(spliterator(), true);
    }
}