RecyclableArrayList Class — netty Architecture

Source Code

common/src/main/java/io/netty/util/internal/RecyclableArrayList.java lines 30–150

public final class RecyclableArrayList extends ArrayList<Object> {

    private static final long serialVersionUID = -8605125654176467947L;

    private static final int DEFAULT_INITIAL_CAPACITY = 8;

    private static final Recycler<RecyclableArrayList> RECYCLER =
            new Recycler<RecyclableArrayList>() {
                @Override
                protected RecyclableArrayList newObject(Handle<RecyclableArrayList> handle) {
                    return new RecyclableArrayList(handle);
                }
            };

    private boolean insertSinceRecycled;

    /**
     * Create a new empty {@link RecyclableArrayList} instance
     */
    public static RecyclableArrayList newInstance() {
        return newInstance(DEFAULT_INITIAL_CAPACITY);
    }

    /**
     * Create a new empty {@link RecyclableArrayList} instance with the given capacity.
     */
    public static RecyclableArrayList newInstance(int minCapacity) {
        RecyclableArrayList ret = RECYCLER.get();
        ret.ensureCapacity(minCapacity);
        return ret;
    }

    private final Handle<RecyclableArrayList> handle;

    private RecyclableArrayList(Handle<RecyclableArrayList> handle) {
        this(handle, DEFAULT_INITIAL_CAPACITY);
    }

    private RecyclableArrayList(Handle<RecyclableArrayList> handle, int initialCapacity) {
        super(initialCapacity);
        this.handle = handle;
    }

    @Override
    public boolean addAll(Collection<?> c) {
        checkNullElements(c);
        if (super.addAll(c)) {
            insertSinceRecycled = true;
            return true;
        }
        return false;
    }

    @Override
    public boolean addAll(int index, Collection<?> c) {
        checkNullElements(c);
        if (super.addAll(index, c)) {
            insertSinceRecycled = true;
            return true;
        }
        return false;
    }

    private static void checkNullElements(Collection<?> c) {
        if (c instanceof RandomAccess && c instanceof List) {
            // produce less garbage
            List<?> list = (List<?>) c;
            int size = list.size();
            for (int i = 0; i  < size; i++) {
                if (list.get(i) == null) {
                    throw new IllegalArgumentException("c contains null values");
                }
            }
        } else {
            for (Object element: c) {
                if (element == null) {
                    throw new IllegalArgumentException("c contains null values");
                }
            }
        }
    }