一、成员private transient Entry
     
       header = new Entry
      
       (null, null, null);private transient int size = 0;底层维护的是一个Entry链表（双向循环链表）二、LinkedList.Entry类成员E element; //dataEntry
       
         next; //前指针Entry
        
          previous; //后指针三、方法1、public LinkedList() {header.next = header.previous = header;}该方法构造了一个新的Entry链表，前后指针都指向自身2、public E getFirst() {if (size==0)throw new NoSuchElementException();return header.next.element;}获取链表中第一个元素3、public E getLast() {if (size==0)throw new NoSuchElementException();return header.previous.element;}获取链表中最后一个元素4、private E remove(Entry
         
           e) {if (e == header)throw new NoSuchElementException();E result = e.element;e.previous.next = e.next;e.next.previous = e.previous;e.next = e.previous = null;e.element = null;size--;modCount++;return result;}移除链表中的某个元素5、private Entry
          
            addBefore(E e, Entry
           
             entry) {Entry
            
              newEntry = new Entry
             
              (e, entry, entry.previous);newEntry.previous.next = newEntry;newEntry.next.previous = newEntry;size++;modCount++;return newEntry;}插入一个元素 6、public boolean addAll(int index, Collection
               c) {if (index < 0 || index > size)throw new IndexOutOfBoundsException("Index: "+index+", Size: "+size);Object[] a = c.toArray();int numNew = a.length;if (numNew==0)return false;modCount++;Entry
              
                successor = (index==size ? header : entry(index));Entry
               
                 predecessor = successor.previous;for (int i=0; i
                
                  e = new Entry
                 
                  ((E)a[i], successor, predecessor);predecessor.next = e;predecessor = e;}successor.previous = predecessor;size += numNew;return true;}在链表最后面添加7、private Entry
                  
                    entry(int index) {if (index < 0 || index >= size)throw new IndexOutOfBoundsException("Index: "+index+", Size: "+size);Entry
                   
                     e = header;if (index < (size >> 1)) {for (int i = 0; i <= index; i++)e = e.next;} else {for (int i = size; i > index; i--)e = e.previous;}return e;}获得index对应的Entry对象，如果index>size>>1则使用前指针，如果index
                    
                     >1 则使用后指针遍历到索引处8、public int indexOf(Object o) {int index = 0;if (o==null) {for (Entry e = header.next; e != header; e = e.next) {if (e.element==null)return index;index++;}} else {for (Entry e = header.next; e != header; e = e.next) {if (o.equals(e.element))return index;index++;}}return -1;}获取元素对应的索引位置9、public boolean removeLastOccurrence(Object o) {if (o==null) {for (Entry
                     
                       e = header.previous; e != header; e = e.previous) {if (e.element==null) {remove(e);return true;}}} else {for (Entry
                      
                        e = header.previous; e != header; e = e.previous) {if (o.equals(e.element)) {remove(e);return true;}}}return false;}移除最后一次出现的元素10、 private class ListItr implements ListIterator
                       
                         list中用来遍历的iterator类型11、public Iterator
                        
                          descendingIterator() {return new DescendingIterator();}private class DescendingIterator implements Iterator用于倒序遍历的iterator