Java集合之LinkedList详解

LinkedList简介

LinkedList继承了AbstractSequentialList，实现List、Deque、Cloneable、Serializable接口。

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

LinkedList 继承了AbstractSequentialList，实现了List 接口，提供了LinkedList的基本列表操作。

public abstract class AbstractSequentialList<E> extends AbstractList<E> {
          
   }

public interface List<E> extends Collection<E> {
          
   }

LinkedList 实现了Deque 接口，即能将LinkedList当作双端队列使用。

public interface Deque<E> extends Queue<E> {
          
   }

LinkedList 实现了Cloneable接口，覆盖了函数clone()，能克隆。

public interface Cloneable {
          
   
}

LinkedList 实现了java.io.Serializable接口，这意味着LinkedList支持序列化，能通过序列化去传输。

public interface Serializable {
          
   
}

数据结构

public class LinkedList<E>
    extends AbstractSequentialList<E>
    implements List<E>, Deque<E>, Cloneable, java.io.Serializable
{
          
   
    private static final long serialVersionUID = 876323262645176354L;
    
    transient int size = 0;

    transient Node<E> first;

    transient Node<E> last;
}

private static class Node<E> {
          
   
    E item;
    Node<E> next;
    Node<E> prev;

    Node(Node<E> prev, E element, Node<E> next) {
          
   
        this.item = element;
        this.next = next;
        this.prev = prev;
    }
}

构造方法

public LinkedList() {
          
   
}

public LinkedList(Collection<? extends E> c) {
          
   
    this();
    addAll(c);
}

常用方法

add

public boolean add(E e) {
          
   
    linkLast(e);
    return true;
}

void linkLast(E e) {
          
   
    final Node<E> l = last;
    final Node<E> newNode = new Node<>(l, e, null);
    last = newNode;
    if (l == null)
        first = newNode;
    else
        l.next = newNode;
    size++;
    modCount++;
}

remove

public boolean remove(Object o) {
          
   
    if (o == null) {
          
   
        for (Node<E> x = first; x != null; x = x.next) {
          
   
            if (x.item == null) {
          
   
                unlink(x);
                return true;
            }
        }
    } else {
          
   
        for (Node<E> x = first; x != null; x = x.next) {
          
   
            if (o.equals(x.item)) {
          
   
                unlink(x);
                return true;
            }
        }
    }
    return false;
}

E unlink(Node<E> x) {
          
   
    // assert x != null;
    final E element = x.item;
    final Node<E> next = x.next;
    final Node<E> prev = x.prev;

    if (prev == null) {
          
   
        first = next;
    } else {
          
   
        prev.next = next;
        x.prev = null;
    }

    if (next == null) {
          
   
        last = prev;
    } else {
          
   
        next.prev = prev;
        x.next = null;
    }

    x.item = null;
    size--;
    modCount++;
    return element;
}

get

public E get(int index) {
          
   
    checkElementIndex(index);
    return node(index).item;
}

private void checkElementIndex(int index) {
          
   
    if (!isElementIndex(index))
        throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
}

private boolean isElementIndex(int index) {
          
   
    return index >= 0 && index < size;
}

Node<E> node(int index) {
          
   
    // assert isElementIndex(index);

    if (index < (size >> 1)) {
          
   
        Node<E> x = first;
        for (int i = 0; i < index; i++)
            x = x.next;
        return x;
    } else {
          
   
        Node<E> x = last;
        for (int i = size - 1; i > index; i--)
            x = x.prev;
        return x;
    }
}