package lbms.plugins.mldht.utils;
import java.util.*;
/**
* similar to the empty Collections instances but allows writes too and simply discards them.
*/
public class Blackhole<E> implements List<E>, Queue<E>, Set<E>, RandomAccess {
public static final Blackhole<?> SINGLETON = new Blackhole<>();
@Override
public boolean offer(E e) {
return true;
}
@Override
public E remove() {
throw new NoSuchElementException();
}
@Override
public E poll() {
return null;
}
@Override
public E element() {
return null;
}
@Override
public E peek() {
return null;
}
@Override
public int size() {
return 0;
}
@Override
public boolean isEmpty() {
return true;
}
@Override
public boolean contains(Object o) {
return false;
}
@Override
public Iterator<E> iterator() {
return Collections.EMPTY_LIST.iterator();
}
@Override
public Object[] toArray() {
return new Object[0];
}
@Override
public <T> T[] toArray(T[] a) {
return a;
}
@Override
public boolean add(E e) {
return true;
}
@Override
public boolean remove(Object o) {
return false;
}
@Override
public boolean containsAll(Collection<?> c) {
return false;
}
@Override
public boolean addAll(Collection<? extends E> c) {
return true;
}
@Override
public boolean addAll(int index, Collection<? extends E> c) {
return true;
}
@Override
public boolean removeAll(Collection<?> c) {
return false;
}
@Override
public boolean retainAll(Collection<?> c) {
return false;
}
@Override
public void clear() {}
@Override
public E get(int index) {
throw new IndexOutOfBoundsException("Index: "+index);
}
@Override
public E set(int index, E element) {
return null;
}
@Override
public void add(int index, E element) {
}
@Override
public E remove(int index) {
return null;
}
@Override
public int indexOf(Object o) {
return -1;
}
@Override
public int lastIndexOf(Object o) {
return -1;
}
@Override
public ListIterator<E> listIterator() {
return Collections.EMPTY_LIST.listIterator();
}
@Override
public ListIterator<E> listIterator(int index) {
return Collections.EMPTY_LIST.listIterator();
}
@Override
public List<E> subList(int fromIndex, int toIndex) {
return this;
}
@Override
public Spliterator<E> spliterator() {
// TODO Auto-generated method stub
return List.super.spliterator();
}
}