int lastRet = -1; // index of last element returned; -1 if no such 

        int expectedModCount = modCount; 

        Itr() {}        // 假设游标不等于size 代表还有下一个元素        public boolean hasNext() {            return cursor != size; 

        }       //        @SuppressWarnings("unchecked") 

        public E next() { 

            checkForComodification();            int i = cursor; 

            // 在此处判别以后游标是超过了数组有效元素个数 

            if (i >= size) 

                throw new NoSuchElementException();            Object[] elementData = ArrayList.this.elementData;            //反省能否数组越界 

            if (i >= elementData.length) 

                throw new ConcurrentModificationException();            cursor = i + 1; 

            // 更新lastRet游标为以后数组下标 

            return (E) elementData[lastRet = i]; 

        }        public void remove() {         // 反省删除元素下标能否合法 

            if (lastRet < 0) 

                throw new IllegalStateException();            checkForComodification();            try {            // 删除原数组中制定下标元素 

                ArrayList.this.remove(lastRet);                //更新游标 

                cursor = lastRet;                lastRet = -1; 

                expectedModCount = modCount;            } catch (IndexOutOfBoundsException ex) {                throw new ConcurrentModificationException();            }        }       } 

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