ArrayList
实现和继承的类和接口
public class ArrayList extends AbstractList
implements List, RandomAccess, Cloneable, java.io.Serializable
AbstractList继承AbstractCollection
域
/**
* The array buffer into which the elements of the ArrayList are stored.
* The capacity of the ArrayList is the length of this array buffer.
*/
private transient Object[] elementData;
/**
* The size of the ArrayList (the number of elements it contains).
*
* @serial
*/
private int size;
elementData是底层存储的数组，使用了瞬时关键字，序列化的时候是真个数组对象序列化，而是将元素一个一个序列化，具体可看writeobject方法，而size是list中实际包含的元素的个数，
fast-fail的域
modCount继承自AbstractList，任何对list的修改调用modCount都递增，在迭代器中每次都会检查这个值是否与期望的一致，如果不一致就会抛出并发修改异常，所以不能直接在迭代中直接调用lisst的修改方法，迭代器中的改变list的方法会同时改变期望值，所以可以在迭代中调用。但是多线程的修改，两种方式都是不行的
扩容
/**
* Increases the capacity of this ArrayList instance, if
* necessary, to ensure that it can hold at least the number of elements
* specified by the minimum capacity argument.
*
* @param minCapacity the desired minimum capacity
*/
public void ensureCapacity(int minCapacity) {
if (minCapacity > 0)
ensureCapacityInternal(minCapacity);
}
private void ensureCapacityInternal(int minCapacity) {
modCount++;
// overflow-conscious code
if (minCapacity - elementData.length > 0)
grow(minCapacity);
}
/**
* The maximum size of array to allocate.
* Some VMs reserve some header words in an array.
* Attempts to allocate larger arrays may result in
* OutOfMemoryError: Requested array size exceeds VM limit
*/
private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
/**
* Increases the capacity to ensure that it can hold at least the
* number of elements specified by the minimum capacity argument.
*
* @param minCapacity the desired minimum capacity
*/
private void grow(int minCapacity) {
// overflow-conscious code
int oldCapacity = elementData.length;
int newCapacity = oldCapacity + (oldCapacity >> 1);
if (newCapacity - minCapacity < 0)
newCapacity = minCapacity;
if (newCapacity - MAX_ARRAY_SIZE > 0)
newCapacity = hugeCapacity(minCapacity);
// minCapacity is usually close to size, so this is a win:
elementData = Arrays.copyOf(elementData, newCapacity);
}
private static int hugeCapacity(int minCapacity) {
if (minCapacity < 0) // overflow
throw new OutOfMemoryError();
return (minCapacity > MAX_ARRAY_SIZE) ?
Integer.MAX_VALUE :
MAX_ARRAY_SIZE;
}
当size到达length时，一般是增大到3/2, 1.7增加了上限，大量使用Arrays.copyOf, 对于大数据量，最好可以先指定list大小创建，避免垃圾回收影响
remove(Object o)时，先搜索到index，然后调fastremove（index），省掉remove（index）中的检查index是否存在的部分并且不返回删除的对象的引用
remove方法参数用Object，因为调用了equals方法，containAll方法用Collection, addAll方法用Collection,add方法用E,注意这些泛型接口的设计
用sublist来调用range相关的方法，底层还是用来的list
ListIterator可以往回迭代
其他可以看看http://www.cnblogs.com/hzmark/archive/2012/12/19/ArrayList.html