LinkedList ArrayList 比较

小结：

1、不是同步的，多线程情况下的处理

   List list = Collections.synchronizedList(new LinkedList(...));

2、

快速失败、并发修改异常

3、

LinkedList (Java Platform SE 8 ) https://docs.oracle.com/javase/8/docs/api/java/util/LinkedList.html

ArrayList (Java Platform SE 8 ) https://docs.oracle.com/javase/8/docs/api/java/util/ArrayList.html

@0

compact1, compact2, compact3

java.util

Class ArrayList<E>

• java.lang.Object
• • java.util.AbstractCollection<E>
  • • java.util.AbstractList<E>
    • • java.util.ArrayList<E>

• All Implemented Interfaces:

  Serializable, Cloneable, Iterable<E>, Collection<E>, List<E>, RandomAccess

  Direct Known Subclasses:

  AttributeList, RoleList, RoleUnresolvedList

  ---

  public class ArrayList<E>
  extends AbstractList<E>
  implements List<E>, RandomAccess, Cloneable, Serializable

compact1, compact2, compact3

java.util

Class LinkedList<E>

• java.lang.Object
• • java.util.AbstractCollection<E>
  • • java.util.AbstractList<E>
    • • java.util.AbstractSequentialList<E>
      • • java.util.LinkedList<E>

• Type Parameters:

  E - the type of elements held in this collection

  All Implemented Interfaces:

  Serializable, Cloneable, Iterable<E>, Collection<E>, Deque<E>, List<E>, Queue<E>

  ---

  public class LinkedList<E>
  extends AbstractSequentialList<E>
  implements List<E>, Deque<E>, Cloneable, Serializable

@1

Note that this implementation is not synchronized. If multiple threads access a linked list concurrently, and at least one of the threads modifies the list structurally, it must be synchronized externally. (A structural modification is any operation that adds or deletes one or more elements; merely setting the value of an element is not a structural modification.) This is typically accomplished by synchronizing on some object that naturally encapsulates the list. If no such object exists, the list should be "wrapped" using the Collections.synchronizedList method. This is best done at creation time, to prevent accidental unsynchronized access to the list:

   List list = Collections.synchronizedList(new LinkedList(...));

Note that this implementation is not synchronized. If multiple threads access an ArrayList instance concurrently, and at least one of the threads modifies the list structurally, it must be synchronized externally. (A structural modification is any operation that adds or deletes one or more elements, or explicitly resizes the backing array; merely setting the value of an element is not a structural modification.) This is typically accomplished by synchronizing on some object that naturally encapsulates the list. If no such object exists, the list should be "wrapped" using the Collections.synchronizedList method. This is best done at creation time, to prevent accidental unsynchronized access to the list:

   List list = Collections.synchronizedList(new ArrayList(...));

@2

The iterators returned by this class's iterator and listIterator methods are fail-fast: if the list is structurally modified at any time after the iterator is created, in any way except through the iterator's own remove or add methods, the iterator will throw aConcurrentModificationException. Thus, in the face of concurrent modification, the iterator fails quickly and cleanly, rather than risking arbitrary, non-deterministic behavior at an undetermined time in the future.

Note that the fail-fast behavior of an iterator cannot be guaranteed as it is, generally speaking, impossible to make any hard guarantees in the presence of unsynchronized concurrent modification. Fail-fast iterators throw ConcurrentModificationExceptionon a best-effort basis. Therefore, it would be wrong to write a program that depended on this exception for its correctness: the fail-fast behavior of iterators should be used only to detect bugs.

@3

public class LinkedList<E>
extends AbstractSequentialList<E>
implements List<E>, Deque<E>, Cloneable, Serializable

Doubly-linked list implementation of the List and Deque interfaces. Implements all optional list operations, and permits all elements (including null).

All of the operations perform as could be expected for a doubly-linked list. Operations that index into the list will traverse the list from the beginning or the end, whichever is closer to the specified index.

public class ArrayList<E>
extends AbstractList<E>
implements List<E>, RandomAccess, Cloneable, Serializable

Resizable-array implementation of the List interface. Implements all optional list operations, and permits all elements, including null. In addition to implementing the List interface, this class provides methods to manipulate the size of the array that is used internally to store the list. (This class is roughly equivalent to Vector, except that it is unsynchronized.)

The size, isEmpty, get, set, iterator, and listIterator operations run in constant time. The add operation runs in amortized constant time, that is, adding n elements requires O(n) time. All of the other operations run in linear time (roughly speaking). The constant factor is low compared to that for the LinkedList implementation.

Each ArrayList instance has a capacity. The capacity is the size of the array used to store the elements in the list. It is always at least as large as the list size. As elements are added to an ArrayList, its capacity grows automatically. The details of the growth policy are not specified beyond the fact that adding an element has constant amortized time cost.

An application can increase the capacity of an ArrayList instance before adding a large number of elements using the ensureCapacity operation. This may reduce the amount of incremental reallocation.

java集合之ArrayList源码解读 https://mp.weixin.qq.com/s/dy98Y-LyQw1BbbH3_X7nBw

// ArrayList动态扩容机制的核心
    private void grow(int minCapacity) {
        // 可能存在整型溢出
        int oldCapacity = elementData.length;
        // 容量默认扩大1.5倍
        int newCapacity = oldCapacity + (oldCapacity >> 1);
        if (newCapacity - minCapacity < 0)
            // 可能1：newCapacity<0整型溢出
            // 可能2：newCapacity<minCapacity
            newCapacity = minCapacity;
        if (newCapacity - MAX_ARRAY_SIZE > 0)
            newCapacity = hugeCapacity(minCapacity);
        // 数组深拷贝
        elementData = Arrays.copyOf(elementData, newCapacity);
    }

Java集合源码分析（一）ArrayList - LanceToBigData - 博客园 https://www.cnblogs.com/zhangyinhua/p/7687377.html

深入分析Java的序列化与反序列化-HollisChuang's Blog https://www.hollischuang.com/archives/1140