迭代器

1. 代码
   1. 节点：单链表节点LinkNode 
   2. 链表：单链表 -->额外方法：getIterator()
      

      1. public class IteratorLinkList extends List {
             static LinkNode first = null;
             
             public LinkNode getFirst(){
                 return first;
             }
             
             public  void setFirst(LinkNode first) {
                 IteratorLinkList.first = first;
             }
         
             public boolean isEmpty() {
                 return first==null;
             }
             public void  insertFirst(LinkNode o1) {// 头插法
                 if(isEmpty()) {
                     first= o1;
                     return;
                 }
                 o1.next = first;
                 first = o1;
             }
              
             // 在指定节点后插入新节点
             public static void insertAfter(LinkNode o1, LinkNode o2) {
                 LinkNode current = first;
                 LinkNode previous = null;
                 while(current!=null){
                     if(current.iData == o1.iData && current.dData == o1.dData){
                         o2.next = current;
                         previous.next = o2;
                         return;
                     }
                     previous = current;
                     current = current.next;
                 }
                 throw new RuntimeException("没有找到该节点");
             }
             public   LinkNode  deleteFirst() {// 删除头节点
                 if(isEmpty()) {
                     throw new RuntimeException("链表为空无法进行删除操作");
                 }
                 LinkNode temp = first;
                 first= first.next; 
                 return temp;
             }
             // 显示链表
             public void displayList() {
                 LinkNode current = first;
                 System.out.println("Display from Front--->End");
                 while(current!=null){
                     System.out.print(current.iData + "  "+ current.dData+"  ");
                     System.out.println();
                     current= current.next;
                 }
             }
             // 找到指定节点
             public static LinkNode findNode(LinkNode o) {
                 LinkNode current = first;
                 while(current!=null){
                     if(current.iData == o.iData && current.dData == o.dData){
                         return current;
                     }
                     current = current.next;
                 }
                 throw new RuntimeException("没有找到该节点");
             }
             // 删除指定节点
             public void deleteNode(LinkNode o) {
                 if(isEmpty()) {
                     throw new RuntimeException("链表为空无法进行删除操作");
                 }
                 LinkNode current = first;
                 LinkNode previous = null;
                 while(current!=null){
                     if(current.iData == o.iData && current.dData == o.dData){
                         previous.next = current.next;
                         return;
                     }
                     previous = current;
                     current = current.next;
                 }
                 throw new RuntimeException("没有找到该节点");
             }
                public ListIterator getIterator()  // return iterator
                   {
                   return new ListIterator(this);  // initialized with
                   }  
         }

   3. 迭代器：

      • public class ListIterator {
            //current link
            private LinkNode current;
            //previous link
            private LinkNode previous;
            //the  target link list
            private IteratorLinkList ourList;
            
            
            public ListIterator(IteratorLinkList ourList) {
                super();
                this.ourList = ourList;
            }
            //reset the iterator :let it start at first
            public void reset(){
                current = ourList.getFirst();
                previous = null;
            }
            public boolean atEnd(){//whether at the end of target linklist
                return current.next==null;
            }
            public void nextLink() {        // step to next link
                previous = current;
                current = current.next;
            }
            public LinkNode getCurrent()  {     // get current link
                return current;
            }
             public void insertAfter(LinkNode dd){//insert after current link
                 if( ourList.isEmpty()) {
                     ourList.setFirst(dd);
                     reset();
                 } 
                 dd.next = current.next;
                 current.next = dd;
                 nextLink();
             }
             public void insertBefore(LinkNode dd){//insert before current link
                 if( ourList.isEmpty()) {// the list is empty
                     ourList.setFirst(dd);
                     reset();
                 } if(previous==null){// there is only one item in the list
                     ourList.setFirst(dd);
                     dd.next = current;
                     reset();
                 }else{// there is more than one item in the list
                    dd.next = current;
                    previous.next = dd;
                    current = dd;
                 }
             }
             public LinkNode deleteCurrent() {   // delete item at current
                 LinkNode temp = current;
                 if( ourList.isEmpty()) {// the list is empty
                     throw new RuntimeException("The List is empty ,could not be deleted any more");
                 } if(previous==null){// there is only one item in the list
                     ourList.setFirst(null); 
                     reset();
                 }else{// there is more than one item in the list
                    previous.next = current.next;
                    if( atEnd() )
                        reset();
                     else
                        current = current.next;
                 }
                 return temp;
             }
        }

         

        迭代器插入节点：在当前节点之后插入新的节点

      • 基于单链表的迭代器:

      • ListIterator

      • 
      • 

        方法总结:

         

      • 当前链表没有任何节点

         

         

        当前链表节点数>1