/*
 * Copyright (c) 2016 Goldman Sachs.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * and Eclipse Distribution License v. 1.0 which accompany this distribution.
 * The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 */

package org.eclipse.collections.impl.set.fixed;

import java.io.Serializable;
import java.util.Collection;
import java.util.Comparator;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.Set;

import org.eclipse.collections.api.block.function.Function;
import org.eclipse.collections.api.block.procedure.Procedure;
import org.eclipse.collections.api.block.procedure.Procedure2;
import org.eclipse.collections.api.block.procedure.primitive.ObjectIntProcedure;
import org.eclipse.collections.api.ordered.OrderedIterable;
import org.eclipse.collections.api.set.MutableSet;
import org.eclipse.collections.api.tuple.Pair;
import org.eclipse.collections.impl.EmptyIterator;
import org.eclipse.collections.impl.factory.Sets;

This class is a memory efficient list with no elements. It is created by calling Lists.fixedSize.of() which actually returns a singleton instance.
/** * This class is a memory efficient list with no elements. It is created by calling Lists.fixedSize.of() which * actually returns a singleton instance. */
final class EmptySet<T> extends AbstractMemoryEfficientMutableSet<T> implements Serializable { private static final long serialVersionUID = 1L; private Object readResolve() { return Sets.fixedSize.of(); } // Weird implementation of clone() is ok on final classes @Override public EmptySet<T> clone() { return this; } @Override public int size() { return 0; } @Override public boolean contains(Object obj) { return false; } @Override public T getFirst() { return null; } @Override public T getLast() { return null; } @Override public T getOnly() { throw new IllegalStateException("Size must be 1 but was " + this.size()); } @Override public void each(Procedure<? super T> procedure) { } @Override public void forEachWithIndex(ObjectIntProcedure<? super T> objectIntProcedure) { } @Override public <P> void forEachWith(Procedure2<? super T, ? super P> procedure, P parameter) { } @Override public Iterator<T> iterator() { return EmptyIterator.getInstance(); } @Override public boolean equals(Object other) { if (other == this) { return true; } if (!(other instanceof Set)) { return false; } Set<?> set = (Set<?>) other; return set.isEmpty(); } @Override public int hashCode() { return 0; } @Override public T min(Comparator<? super T> comparator) { throw new NoSuchElementException(); } @Override public T max(Comparator<? super T> comparator) { throw new NoSuchElementException(); } @Override public T min() { throw new NoSuchElementException(); } @Override public T max() { throw new NoSuchElementException(); } @Override public <V extends Comparable<? super V>> T minBy(Function<? super T, ? extends V> function) { throw new NoSuchElementException(); } @Override public <V extends Comparable<? super V>> T maxBy(Function<? super T, ? extends V> function) { throw new NoSuchElementException(); }
Deprecated:in 6.0. Use OrderedIterable.zip(Iterable) instead.
/** * @deprecated in 6.0. Use {@link OrderedIterable#zip(Iterable)} instead. */
@Deprecated @Override public <S> MutableSet<Pair<T, S>> zip(Iterable<S> that) { return Sets.fixedSize.of(); } @Override public <S, R extends Collection<Pair<T, S>>> R zip(Iterable<S> that, R target) { return target; }
Deprecated:in 6.0. Use OrderedIterable.zipWithIndex() instead.
/** * @deprecated in 6.0. Use {@link OrderedIterable#zipWithIndex()} instead. */
@Deprecated @Override public MutableSet<Pair<T, Integer>> zipWithIndex() { return Sets.fixedSize.of(); } @Override public <R extends Collection<Pair<T, Integer>>> R zipWithIndex(R target) { return target; } @Override public MutableSet<T> with(T element) { return new SingletonSet<>(element); } @Override public MutableSet<T> without(T element) { return this; } }