ArrayList

extends AbstractList<E> implements List<E>, RandomAccess, Cloneable, java.io.Serializable

• 容器实体

transient Object[] elementData

扩容

• 倍数：1.5n

// 1.8
int newCapacity = oldCapacity + (oldCapacity >> 1);

• 方式

// 1.8
elementData = Arrays.copyOf(elementData, newCapacity);