// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc.  All rights reserved.
// https://developers.google.com/protocol-buffers/
//
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// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
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// contributors may be used to endorse or promote products derived from
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package com.google.protobuf;

import com.google.protobuf.Internal.ProtobufList;
import java.util.AbstractList;
import java.util.Collection;
import java.util.List;
import java.util.RandomAccess;

An abstract implementation of ProtobufList which manages mutability semantics. All mutate methods must check if the list is mutable before proceeding. Subclasses must invoke ensureIsMutable() manually when overriding those methods. 
This implementation assumes all subclasses are array based, supporting random access.
/**
 * An abstract implementation of {@link ProtobufList} which manages mutability semantics. All mutate
 * methods must check if the list is mutable before proceeding. Subclasses must invoke {@link
 * #ensureIsMutable()} manually when overriding those methods.
 *
 * <p>This implementation assumes all subclasses are array based, supporting random access.
 */
abstract class AbstractProtobufList<E> extends AbstractList<E> implements ProtobufList<E> {

  protected static final int DEFAULT_CAPACITY = 10;

  
Whether or not this list is modifiable. /** Whether or not this list is modifiable. */
  private boolean isMutable;

  
Constructs a mutable list by default. /** Constructs a mutable list by default. */
  AbstractProtobufList() {
    isMutable = true;
  }

  @Override
  public boolean equals(Object o) {
    if (o == this) {
      return true;
    }
    if (!(o instanceof List)) {
      return false;
    }
    // Handle lists that do not support RandomAccess as efficiently as possible by using an iterator
    // based approach in our super class. Otherwise our index based approach will avoid those
    // allocations.
    if (!(o instanceof RandomAccess)) {
      return super.equals(o);
    }

    List<?> other = (List<?>) o;
    final int size = size();
    if (size != other.size()) {
      return false;
    }
    for (int i = 0; i < size; i++) {
      if (!get(i).equals(other.get(i))) {
        return false;
      }
    }
    return true;
  }

  @Override
  public int hashCode() {
    final int size = size();
    int hashCode = 1;
    for (int i = 0; i < size; i++) {
      hashCode = (31 * hashCode) + get(i).hashCode();
    }
    return hashCode;
  }

  @Override
  public boolean add(E e) {
    ensureIsMutable();
    return super.add(e);
  }

  @Override
  public void add(int index, E element) {
    ensureIsMutable();
    super.add(index, element);
  }

  @Override
  public boolean addAll(Collection<? extends E> c) {
    ensureIsMutable();
    return super.addAll(c);
  }

  @Override
  public boolean addAll(int index, Collection<? extends E> c) {
    ensureIsMutable();
    return super.addAll(index, c);
  }

  @Override
  public void clear() {
    ensureIsMutable();
    super.clear();
  }

  @Override
  public boolean isModifiable() {
    return isMutable;
  }

  @Override
  public final void makeImmutable() {
    isMutable = false;
  }

  @Override
  public E remove(int index) {
    ensureIsMutable();
    return super.remove(index);
  }

  @Override
  public boolean remove(Object o) {
    ensureIsMutable();
    return super.remove(o);
  }

  @Override
  public boolean removeAll(Collection<?> c) {
    ensureIsMutable();
    return super.removeAll(c);
  }

  @Override
  public boolean retainAll(Collection<?> c) {
    ensureIsMutable();
    return super.retainAll(c);
  }

  @Override
  public E set(int index, E element) {
    ensureIsMutable();
    return super.set(index, element);
  }

  
Throws an UnsupportedOperationException if the list is immutable. Subclasses are responsible for invoking this method on mutate operations. /**
   * Throws an {@link UnsupportedOperationException} if the list is immutable. Subclasses are
   * responsible for invoking this method on mutate operations.
   */
  protected void ensureIsMutable() {
    if (!isMutable) {
      throw new UnsupportedOperationException();
    }
  }
}