guava/src/com/google/common/collect/RegularImmutableList.java

/*
 * Copyright (C) 2009 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 com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.VisibleForTesting;
import java.util.Spliterator;
import java.util.Spliterators;

/**
 * Implementation of {@link ImmutableList} backed by a simple array.
 *
 * @author Kevin Bourrillion
 */
@GwtCompatible(serializable = true, emulated = true)
@SuppressWarnings("serial") // uses writeReplace(), not default serialization
class RegularImmutableList<E> extends ImmutableList<E> {
  static final ImmutableList<Object> EMPTY = new RegularImmutableList<>(new Object[0]);

  @VisibleForTesting final transient Object[] array;

  RegularImmutableList(Object[] array) {
    this.array = array;
  }

  @Override
  public int size() {
    return array.length;
  }

  @Override
  boolean isPartialView() {
    return false;
  }

  @Override
  Object[] internalArray() {
    return array;
  }

  @Override
  int internalArrayStart() {
    return 0;
  }

  @Override
  int internalArrayEnd() {
    return array.length;
  }

  @Override
  int copyIntoArray(Object[] dst, int dstOff) {
    System.arraycopy(array, 0, dst, dstOff, array.length);
    return dstOff + array.length;
  }

  // The fake cast to E is safe because the creation methods only allow E's
  @Override
  @SuppressWarnings("unchecked")
  public E get(int index) {
    return (E) array[index];
  }

  @SuppressWarnings("unchecked")
  @Override
  public UnmodifiableListIterator<E> listIterator(int index) {
    // for performance
    // The fake cast to E is safe because the creation methods only allow E's
    return (UnmodifiableListIterator<E>) Iterators.forArray(array, 0, array.length, index);
  }

  @Override
  public Spliterator<E> spliterator() {
    return Spliterators.spliterator(array, SPLITERATOR_CHARACTERISTICS);
  }

  // TODO(lowasser): benchmark optimizations for equals() and see if they're worthwhile
}