Class ArrayList

lib/java/util/ArrayList.java:31–708

ArrayList is an implementation of List, backed by an array. All optional operations adding, removing, and replacing are supported. The elements can be any objects. @since 1.2

 * @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 size;

    private transient E[] array;

    /**
     * Constructs a new instance of {@code ArrayList} with ten capacity.
     */
    public ArrayList() {
        this(10);
    }

    /**
     * Constructs a new instance of {@code ArrayList} with the specified
     * capacity.
     * 
     * @param capacity
     *            the initial capacity of this {@code ArrayList}.
     */
    public ArrayList(int capacity) {
        if (capacity < 0) {
            throw new IllegalArgumentException();
        }
        firstIndex = size = 0;
        array = newElementArray(capacity);
    }

    /**
     * Constructs a new instance of {@code ArrayList} containing the elements of
     * the specified collection. The initial size of the {@code ArrayList} will
     * be 10% larger than the size of the specified collection.
     * 
     * @param collection
     *            the collection of elements to add.
     */
    public ArrayList(Collection<? extends E> collection) {
        firstIndex = 0;
        Object[] objects = collection.toArray();
        size = objects.length;

        // REVIEW: Created 2 array copies of the original collection here
        //         Could be better to use the collection iterator and
        //         copy once?
        array = newElementArray(size + (size / 10));
        System.arraycopy(objects, 0, array, 0, size);
        modCount = 1;
    }

    @SuppressWarnings("unchecked")
    private E[] newElementArray(int size) {
        return (E[]) new Object[size];
    }