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/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You 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 java.util;


import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.lang.reflect.Array;

/**
 * ArrayList is an implementation of List, backed by an array. All optional
 * operations are supported, adding, removing, and replacing. The elements can
 * be any objects.
 * @since 1.2
 */
public class ArrayList<E> extends AbstractList<E> implements List<E>, Cloneable,
    Serializable, RandomAccess {

  private static final long serialVersionUID = 8683452581122892189L;

  private transient int firstIndex;
    
    private transient int lastIndex;

  private transient E[] array;

  /**
   * Constructs a new instance of ArrayList with zero capacity.
   */
  public ArrayList() {
    this(0);
  }

  /**
   * Constructs a new instance of ArrayList with the specified capacity.
   * 
   * @param capacity
   *            the initial capacity of this ArrayList
   */
  public ArrayList(int capacity) {
    firstIndex = lastIndex = 0;
    try {
      array = newElementArray(capacity);
    } catch (NegativeArraySizeException e) {
      throw new IllegalArgumentException();
    }
  }

  /**
   * Constructs a new instance of ArrayList containing the elements in the
   * specified collection. The ArrayList will have an initial capacity which
   * is 110% of the size of the collection. The order of the elements in this
   * ArrayList is the order they are returned by the collection iterator.
   * 
   * @param collection
   *            the collection of elements to add
   */
  public ArrayList(Collection<? extends E> collection) {
    int size = collection.size();
    firstIndex = lastIndex = 0;
    array = newElementArray(size + (size / 10));
    addAll(collection);
  }
    
    @SuppressWarnings("unchecked")
    private E[] newElementArray(int size) {
        return (E[])new Object[size];
    }

  /**
   * Inserts the specified object into this ArrayList at the specified
   * location. The object is inserted before any previous element at the
   * specified location. If the location is equal to the size of this
   * ArrayList, the object is added at the end.
   * 
   * @param location
   *            the index at which to insert
   * @param object
   *            the object to add
   * 
   * @exception IndexOutOfBoundsException
   *                when <code>location < 0 || >= size()</code>
   */
  @Override
    public void add(int location, E object) {
    int size = size();
    if (0 < location && location < size) {
      if (firstIndex == 0 && lastIndex == array.length) {
        growForInsert(location, 1);
      } else if ((location < size / 2 && firstIndex > 0)
          || lastIndex == array.length) {
        System.arraycopy(array, firstIndex, array, --firstIndex,
            location);
      } else {
        int index = location + firstIndex;
        System.arraycopy(array, index, array, index + 1, size
            - location);
        lastIndex++;
      }
      array[location + firstIndex] = object;
    } else if (location == 0) {
      if (firstIndex == 0) {
                growAtFront(1);
            }
      array[--firstIndex] = object;
    } else if (location == size) {
      if (lastIndex == array.length) {
                growAtEnd(1);
            }
      array[lastIndex++] = object;
    } else {
            throw new IndexOutOfBoundsException();
        }

    modCount++;
  }

  /**
   * Adds the specified object at the end of this ArrayList.
   * 
   * @param object
   *            the object to add
   * @return true
   */
  @Override
    public boolean add(E object) {
    if (lastIndex == array.length) {
            growAtEnd(1);
        }
    array[lastIndex++] = object;
    modCount++;
    return true;
  }

  /**
     * Inserts the objects in the specified Collection at the specified location
     * in this ArrayList. The objects are added in the order they are returned
     * from the Collection iterator.
     * 
     * @param location the index at which to insert
     * @param collection the Collection of objects
     * @return true if this ArrayList is modified, false otherwise
     * 
     * @exception IndexOutOfBoundsException when
     *            <code>location < 0 || > size()</code>
     */
    @Override
    public boolean addAll(int location, Collection<? extends E> collection) {
        int size = size();
        if (location < 0 || location > size) {
            throw new IndexOutOfBoundsException();
        }
        int growSize = collection.size();
        if (0 < location && location < size) {
            if (array.length - size < growSize) {
                growForInsert(location, growSize);
            } else if ((location < size / 2 && firstIndex > 0)
                    || lastIndex > array.length - growSize) {
                int newFirst = firstIndex - growSize;
                if (newFirst < 0) {
                    int index = location + firstIndex;
                    System.arraycopy(array, index, array, index - newFirst,
                            size - location);
                    lastIndex -= newFirst;
                    newFirst = 0;
                }
                System.arraycopy(array, firstIndex, array, newFirst, location);
                firstIndex = newFirst;
            } else {
                int index = location + firstIndex;
                System.arraycopy(array, index, array, index + growSize, size
                        - location);
                lastIndex += growSize;
            }
        } else if (location == 0) {
            growAtFront(growSize);
            firstIndex -= growSize;
        } else if (location == size) {
            if (lastIndex > array.length - growSize) {
                growAtEnd(growSize);
            }
            lastIndex += growSize;
        }

        if (growSize > 0) {
            Iterator<? extends E> it = collection.iterator();
            int index = location + firstIndex;
            int end = index + growSize;
            while (index < end) {
                array[index++] = it.next();
            }
            modCount++;
            return true;
        }
        return false;
    }

  /**
   * Adds the objects in the specified Collection to this ArrayList.
   * 
   * @param collection
   *            the Collection of objects
   * @return true if this ArrayList is modified, false otherwise
   */
  @Override
    public boolean addAll(Collection<? extends E> collection) {
    int growSize = collection.size();
    if (growSize > 0) {
      if (lastIndex > array.length - growSize) {
                growAtEnd(growSize);
            }
      Iterator<? extends E> it = collection.iterator();
      int end = lastIndex + growSize;
      while (lastIndex < end) {
                array[lastIndex++] = it.next();
            }
      modCount++;
      return true;
    }
    return false;
  }

  /**
   * Removes all elements from this ArrayList, leaving it empty.
   * 
   * @see #isEmpty
   * @see #size
   */
  @Override
    public void clear() {
    if (firstIndex != lastIndex) {
      Arrays.fill(array, firstIndex, lastIndex, null);
      firstIndex = lastIndex = 0;
      modCount++;
    }
  }

  /**
   * Answers a new ArrayList with the same elements, size and capacity as this
   * ArrayList.
   * 
   * @return a shallow copy of this ArrayList
   * 
   * @see java.lang.Cloneable
   */
  @Override
    @SuppressWarnings("unchecked")
    public Object clone() {
    try {
      ArrayList<E> newList = (ArrayList<E>) super.clone();
      newList.array = array.clone();
      return newList;
    } catch (CloneNotSupportedException e) {
      return null;
    }
  }

  /**
   * Searches this ArrayList for the specified object.
   * 
   * @param object
   *            the object to search for
   * @return true if <code>object</code> is an element of this ArrayList,
   *         false otherwise
   */
  @Override
    public boolean contains(Object object) {
    if (object != null) {
      for (int i = firstIndex; i < lastIndex; i++) {
                if (object.equals(array[i])) {
                    return true;
                }
            }
    } else {
      for (int i = firstIndex; i < lastIndex; i++) {
                if (array[i] == null) {
                    return true;
                }
            }
    }
    return false;
  }

  /**
   * Ensures that this ArrayList can hold the specified number of elements
   * without growing.
   * 
   * @param minimumCapacity
   *            the minimum number of elements that this ArrayList will hold
   *            before growing
   */
  public void ensureCapacity(int minimumCapacity) {
    if (array.length < minimumCapacity) {
      if (firstIndex > 0) {
                growAtFront(minimumCapacity - array.length);
            } else {
                growAtEnd(minimumCapacity - array.length);
            }
    }
  }

  /**
   * Answers the element at the specified location in this ArrayList.
   * 
   * @param location
   *            the index of the element to return
   * @return the element at the specified index
   * 
   * @exception IndexOutOfBoundsException
   *                when <code>location < 0 || >= size()</code>
   */
  @Override
    public E get(int location) {
    if (0 <= location && location < size()) {
      return array[firstIndex + location];
        }
    throw new IndexOutOfBoundsException();
  }

  private void growAtEnd(int required) {
    int size = size();
    if (firstIndex >= required - (array.length - lastIndex)) {
      int newLast = lastIndex - firstIndex;
      if (size > 0) {
        System.arraycopy(array, firstIndex, array, 0, size);
        int start = newLast < firstIndex ? firstIndex : newLast;
        Arrays.fill(array, start, array.length, null);
      }
      firstIndex = 0;
      lastIndex = newLast;
    } else {
      int increment = size / 2;
      if (required > increment) {
                increment = required;
            }
      if (increment < 12) {
                increment = 12;
            }
      E[] newArray = newElementArray(size + increment);
      if (size > 0) {
                System.arraycopy(array, firstIndex, newArray, firstIndex, size);
            }
      array = newArray;
    }
  }

  private void growAtFront(int required) {
    int size = size();
    if (array.length - lastIndex >= required) {
      int newFirst = array.length - size;
      if (size > 0) {
        System.arraycopy(array, firstIndex, array, newFirst, size);
        int length = firstIndex + size > newFirst ? newFirst
            : firstIndex + size;
        Arrays.fill(array, firstIndex, length, null);
      }
      firstIndex = newFirst;
      lastIndex = array.length;
    } else {
      int increment = size / 2;
      if (required > increment) {
                increment = required;
            }
      if (increment < 12) {
                increment = 12;
            }
      E[] newArray = newElementArray(size + increment);
      if (size > 0) {
                System.arraycopy(array, firstIndex, newArray, newArray.length
            - size, size);
            }
      firstIndex = newArray.length - size;
      lastIndex = newArray.length;
      array = newArray;
    }
  }

  private void growForInsert(int location, int required) {
    int size = size(), increment = size / 2;
    if (required > increment) {
            increment = required;
        }
    if (increment < 12) {
            increment = 12;
        }
    E[] newArray = newElementArray(size + increment);
    if (location < size / 2) {
      int newFirst = newArray.length - (size + required);
      System.arraycopy(array, location, newArray, location + increment,
          size - location);
      System.arraycopy(array, firstIndex, newArray, newFirst, location);
      firstIndex = newFirst;
      lastIndex = newArray.length;
    } else {
      System.arraycopy(array, firstIndex, newArray, 0, location);
      System.arraycopy(array, location, newArray, location + required,
          size - location);
      firstIndex = 0;
      lastIndex += required;
    }
    array = newArray;
  }

  /**
   * Searches this ArrayList for the specified object and returns the index of
   * the first occurrence.
   * 
   * @param object
   *            the object to search for
   * @return the index of the first occurrence of the object
   */
  @Override
    public int indexOf(Object object) {
    if (object != null) {
      for (int i = firstIndex; i < lastIndex; i++) {
                if (object.equals(array[i])) {
                    return i - firstIndex;
                }
            }
    } else {
      for (int i = firstIndex; i < lastIndex; i++) {
                if (array[i] == null) {
                    return i - firstIndex;
                }
            }
    }
    return -1;
  }

  /**
   * Answers if this ArrayList has no elements, a size of zero.
   * 
   * @return true if this ArrayList has no elements, false otherwise
   * 
   * @see #size
   */
  @Override
    public boolean isEmpty() {
    return lastIndex == firstIndex;
  }

  /**
   * Searches this ArrayList for the specified object and returns the index of
   * the last occurrence.
   * 
   * @param object
   *            the object to search for
   * @return the index of the last occurrence of the object
   */
  @Override
    public int lastIndexOf(Object object) {
    if (object != null) {
      for (int i = lastIndex - 1; i >= firstIndex; i--) {
                if (object.equals(array[i])) {
                    return i - firstIndex;
                }
            }
    } else {
      for (int i = lastIndex - 1; i >= firstIndex; i--) {
                if (array[i] == null) {
                    return i - firstIndex;
                }
            }
    }
    return -1;
  }

  /**
   * Removes the object at the specified location from this ArrayList.
   * 
   * @param location
   *            the index of the object to remove
   * @return the removed object
   * 
   * @exception IndexOutOfBoundsException
   *                when <code>location < 0 || >= size()</code>
   */
  @Override
    public E remove(int location) {
    E result;
    int size = size();
    if (0 <= location && location < size) {
      if (location == size - 1) {
        result = array[--lastIndex];
        array[lastIndex] = null;
      } else if (location == 0) {
        result = array[firstIndex];
        array[firstIndex++] = null;
      } else {
        int elementIndex = firstIndex + location;
        result = array[elementIndex];
        if (location < size / 2) {
          System.arraycopy(array, firstIndex, array, firstIndex + 1,
              location);
          array[firstIndex++] = null;
        } else {
          System.arraycopy(array, elementIndex + 1, array,
              elementIndex, size - location - 1);
          array[--lastIndex] = null;
        }
      }
    } else {
            throw new IndexOutOfBoundsException();
        }

    modCount++;
    return result;
  }

  /**
   * Removes the objects in the specified range from the start to the end, but
   * not including the end index.
   * 
   * @param start
   *            the index at which to start removing
   * @param end
   *            the index one past the end of the range to remove
   * 
   * @exception IndexOutOfBoundsException
   *                when <code>start < 0, start > end</code> or
   *                <code>end > size()</code>
   */
  @Override
    protected void removeRange(int start, int end) {
    if (start >= 0 && start <= end && end <= size()) {
      if (start == end) {
                return;
            }
      int size = size();
      if (end == size) {
        Arrays.fill(array, firstIndex + start, lastIndex, null);
        lastIndex = firstIndex + start;
      } else if (start == 0) {
        Arrays.fill(array, firstIndex, firstIndex + end, null);
        firstIndex += end;
      } else {
        System.arraycopy(array, firstIndex + end, array, firstIndex
            + start, size - end);
        int newLast = lastIndex + start - end;
        Arrays.fill(array, newLast, lastIndex, null);
        lastIndex = newLast;
      }
      modCount++;
    } else {
            throw new IndexOutOfBoundsException();
        }
  }

  /**
   * Replaces the element at the specified location in this ArrayList with the
   * specified object.
   * 
   * @param location
   *            the index at which to put the specified object
   * @param object
   *            the object to add
   * @return the previous element at the index
   * 
   * @exception IndexOutOfBoundsException
   *                when <code>location < 0 || >= size()</code>
   */
  @Override
    public E set(int location, E object) {
    if (0 <= location && location < size()) {
      E result = array[firstIndex + location];
      array[firstIndex + location] = object;
      return result;
    }
    throw new IndexOutOfBoundsException();
  }

  /**
   * Answers the number of elements in this ArrayList.
   * 
   * @return the number of elements in this ArrayList
   */
  @Override
    public int size() {
    return lastIndex - firstIndex;
  }

  /**
   * Answers a new array containing all elements contained in this ArrayList.
   * 
   * @return an array of the elements from this ArrayList
   */
  @Override
    public Object[] toArray() {
    int size = size();
    Object[] result = new Object[size];
    System.arraycopy(array, firstIndex, result, 0, size);
    return result;
  }

  /**
   * Answers an array containing all elements contained in this ArrayList. If
   * the specified array is large enough to hold the elements, the specified
   * array is used, otherwise an array of the same type is created. If the
   * specified array is used and is larger than this ArrayList, the array
   * element following the collection elements is set to null.
   * 
   * @param contents
   *            the array
   * @return an array of the elements from this ArrayList
   * 
   * @exception ArrayStoreException
   *                when the type of an element in this ArrayList cannot be
   *                stored in the type of the specified array
   */
  @Override
    @SuppressWarnings("unchecked")
    public <T> T[] toArray(T[] contents) {
    int size = size();
    if (size > contents.length) {
            Class<?> ct = contents.getClass().getComponentType();
      contents = (T[]) Array.newInstance(ct, size);
        }
    System.arraycopy(array, firstIndex, contents, 0, size);
    if (size < contents.length) {
            contents[size] = null;
        }
    return contents;
  }

  /**
   * Sets the capacity of this ArrayList to be the same as the size.
   * 
   * @see #size
   */
  public void trimToSize() {
    int size = size();
    E[] newArray = newElementArray(size);
    System.arraycopy(array, firstIndex, newArray, 0, size);
    array = newArray;
    firstIndex = 0;
    lastIndex = array.length;
  }

  /*
  private static final ObjectStreamField[] serialPersistentFields = { new ObjectStreamField(
      "size", Integer.TYPE) }; //$NON-NLS-1$
  */

  private void writeObject(ObjectOutputStream stream) throws IOException {
    ObjectOutputStream.PutField fields = stream.putFields();
    fields.put("size", size()); //$NON-NLS-1$
    stream.writeFields();
    stream.writeInt(array.length);
    Iterator<?> it = iterator();
    while (it.hasNext()) {
            stream.writeObject(it.next());
        }
  }

  @SuppressWarnings("unchecked")
    private void readObject(ObjectInputStream stream) throws IOException,
      ClassNotFoundException {
    ObjectInputStream.GetField fields = stream.readFields();
    lastIndex = fields.get("size", 0); //$NON-NLS-1$
    array = newElementArray(stream.readInt());
    for (int i = 0; i < lastIndex; i++) {
            array[i] = (E)stream.readObject();
        }
  }
}
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