ArrayList內(nèi)部類訪問(wèn)其成員變量的問(wèn)題

下面是ArrayList的迭代器源碼，我注意到這兩行

 Object[] elementData = ArrayList.this.elementData;
 expectedModCount = modCount;

第一行用的是標(biāo)準(zhǔn)的內(nèi)部類訪問(wèn)外部類成員變量的方法，為何第二行則是直接用變量名，沒(méi)有加“ArrayList.this”?
為何modCount不需要加“ArrayList.this”?不加也能成？

private class Itr implements Iterator<E> {
    int cursor;       // index of next element to return
    int lastRet = -1; // index of last element returned; -1 if no such
    int expectedModCount = modCount;

    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 void remove() {
        if (lastRet < 0)
            throw new IllegalStateException();
        checkForComodification();

        try {
            ArrayList.this.remove(lastRet);
            cursor = lastRet;
            lastRet = -1;
            expectedModCount = modCount;
        } catch (IndexOutOfBoundsException ex) {
            throw new ConcurrentModificationException();
        }
    }