设计模式课程 设计模式精讲 18-3 迭代器模式源码解析

public interface Iterator<E> {
    /**
     * Returns {@code true} if the iteration has more elements.
     * (In other words, returns {@code true} if {@link #next} would
     * return an element rather than throwing an exception.)
     *
     * @return {@code true} if the iteration has more elements
     */
　　//和我们18-2中的isNext有相同的作用
    boolean hasNext();
}

private class Itr implements Iterator<E> {

        public boolean hasNext() {
            return cursor != size;
        }

        @SuppressWarnings("unchecked")
        public E next() {
            checkForComodification();
            int i = cursor;
            if (i >= size)
                throw new NoSuchElementException();
            Object[] elementData = ArrayList.this.elementData;
            if (i >= elementData.length)
                throw new ConcurrentModificationException();
            cursor = i + 1;
            return (E) elementData[lastRet = i];
        }


}

public class DefaultCursor<T> implements Cursor<T> {
//创建了游标迭代器 
private final CursorIterator cursorIterator = new CursorIterator();
 
@Override
    public Iterator<T> iterator() {
        if (iteratorRetrieved) {
            throw new IllegalStateException("Cannot open more than one iterator on a Cursor");
        }
        iteratorRetrieved = true;
        return cursorIterator;
    }
}