数组遍历 和 迭代器遍历的区别

循环数组时候如果要对数组进行add、remove操作，采用 迭代器的遍历，

list的遍历通常有三种方式:

1，普通的数组遍历

 for (int i = 0; i < args.length; i++) {    }

2，加强型数组遍历

for (String string : args) {    }

3，迭代器遍历

while (it.hasNext()) {            type type = (type) it.next();    }

使用数组遍历的过程中不能进行add、remove等改变数组内容的操作，否则会报错；迭代器可以final void checkForComodification() {    if (modCount != expectedModCount)    throw new ConcurrentModificationException();}

因为

array进行add、remove等操作时，array中index后的元素会产生移动

public void add(int index, E element) {    if (index > size || index < 0)        throw new IndexOutOfBoundsException(        "Index: "+index+", Size: "+size);    ensureCapacity(size+1);  // Increments modCount!!    System.arraycopy(elementData, index, elementData, index + 1,             size - index);    elementData[index] = element;    size++;    }

/*     * Private remove method that skips bounds checking and does not     * return the value removed.     */    private void fastRemove(int index) {        modCount++;        int numMoved = size - index - 1;        if (numMoved > 0)            System.arraycopy(elementData, index+1, elementData, index,                             numMoved);        elementData[--size] = null; // Let gc do its work    }

LinkedList内部类 public ListIterator listIterator(int index)

    public E next() {        checkForComodification();        if (nextIndex == size)        throw new NoSuchElementException();        lastReturned = next;        next = next.next;        nextIndex++;        return lastReturned.element;    }

public void add(E e) {        checkForComodification();        lastReturned = header;        addBefore(e, next);        nextIndex++;        expectedModCount++;    }

public void remove() {            checkForComodification();            Entry<E> lastNext = lastReturned.next;            try {                LinkedList.this.remove(lastReturned);            } catch (NoSuchElementException e) {                throw new IllegalStateException();            }        if (next==lastReturned)                next = lastNext;            else        nextIndex--;        lastReturned = header;        expectedModCount++;    }