com.google.common.collect.ImmutableCollection.java Source code

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Here is the source code for com.google.common.collect.ImmutableCollection.java

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/*
 * Copyright (C) 2008 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect;

import static com.google.common.base.Preconditions.checkNotNull;

import java.io.Serializable;
import java.util.AbstractCollection;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;

import javax.annotation.Nullable;

/**
 * GWT emulated version of {@link ImmutableCollection}.
 *
 * @author Jesse Wilson
 */
@SuppressWarnings("serial") // we're overriding default serialization
public abstract class ImmutableCollection<E> extends AbstractCollection<E> implements Serializable {

    static final ImmutableCollection<Object> EMPTY_IMMUTABLE_COLLECTION = new ForwardingImmutableCollection<Object>(
            Collections.emptyList());

    ImmutableCollection() {
    }

    public abstract UnmodifiableIterator<E> iterator();

    public boolean contains(@Nullable Object object) {
        return object != null && super.contains(object);
    }

    public final boolean add(E e) {
        throw new UnsupportedOperationException();
    }

    public final boolean remove(Object object) {
        throw new UnsupportedOperationException();
    }

    public final boolean addAll(Collection<? extends E> newElements) {
        throw new UnsupportedOperationException();
    }

    public final boolean removeAll(Collection<?> oldElements) {
        throw new UnsupportedOperationException();
    }

    public final boolean retainAll(Collection<?> elementsToKeep) {
        throw new UnsupportedOperationException();
    }

    public final void clear() {
        throw new UnsupportedOperationException();
    }

    private transient ImmutableList<E> asList;

    public ImmutableList<E> asList() {
        ImmutableList<E> list = asList;
        return (list == null) ? (asList = createAsList()) : list;
    }

    ImmutableList<E> createAsList() {
        switch (size()) {
        case 0:
            return ImmutableList.of();
        case 1:
            return ImmutableList.of(iterator().next());
        default:
            return new RegularImmutableAsList<E>(this, toArray());
        }
    }

    static <E> ImmutableCollection<E> unsafeDelegate(Collection<E> delegate) {
        return new ForwardingImmutableCollection<E>(delegate);
    }

    boolean isPartialView() {
        return false;
    }

    /**
     * GWT emulated version of {@link ImmutableCollection.Builder}.
     */
    public abstract static class Builder<E> {

        Builder() {
        }

        public abstract Builder<E> add(E element);

        public Builder<E> add(E... elements) {
            checkNotNull(elements); // for GWT
            for (E element : elements) {
                add(checkNotNull(element));
            }
            return this;
        }

        public Builder<E> addAll(Iterable<? extends E> elements) {
            checkNotNull(elements); // for GWT
            for (E element : elements) {
                add(checkNotNull(element));
            }
            return this;
        }

        public Builder<E> addAll(Iterator<? extends E> elements) {
            checkNotNull(elements); // for GWT
            while (elements.hasNext()) {
                add(checkNotNull(elements.next()));
            }
            return this;
        }

        public abstract ImmutableCollection<E> build();
    }
}