Interview question: what are the differences between ArrayList and LinkedList

One 、 Their underlying data structures are different

ArrayList The underlying layer of is implemented by arrays , It can be seen from the source code ：

LinkedList The bottom layer of is based on linked list , Because the linked list is composed of multiple nodes , The cells of the linked list are nodes , Look at the source code ：

Two 、 Two classes implement List Interface , however LinkedList It's also achieved Deque Interface

ArrayList Class implements the List Interface , Take a look at the source code ：

public class ArrayList<E> extends AbstractList<E>
        implements List<E>, RandomAccess, Cloneable, java.io.Serializable
{
  ................

LinkedList Not only has List Interface , It's also achieved Deque Interface , So it can also be used as a double ended queue

public class LinkedList<E>
    extends AbstractSequentialList<E>
    implements List<E>, Deque<E>, Cloneable, java.io.Serializable
{
  ................

3、 ... and 、 Different scenarios

ArrayList The bottom layer is based on the array implementation , So the query is relatively fast ,
Adding and deleting are slow , Because it may involve an expansion operation

LinkedList The bottom layer is based on linked list , So it is more suitable for adding and deleting