importjava.io.BufferedReader;importjava.io.IOException;importjava.io.InputStreamReader;importtest_4_19.system;/*** java链表中迭代器的实现

* 2017年5月2号17:25

*@authorzcj

**/

classLink9

{public longdData;publicLink9 next;public Link9(longdd)

{

dData=dd;

}public voiddisplayLink()

{

System.out.print(dData+ " ");

}

}classLinkList9

{privateLink9 first;publicLinkList9()

{

first= null;

}public Link9 getFirst()//获取链表的first

{returnfirst;

}public void setFirst(Link9 f)//由于在迭代器里面first可能会改变，所以需要LinkList中提供first改变的方法

{

first=f;

}public booleanisEmpty()

{return first==null;

}publicListIterator getIterator()

{return new ListIterator(this);

}public voiddispalyList()

{

Link9 current=first;while(current != null)

{

current.displayLink();

current=current.next;

}

System.out.println("");

}

}classListIterator

{privateLink9 current;privateLink9 previous;privateLinkList9 ourList;publicListIterator(LinkList9 list)

{

ourList=list;

reset();

}public void reset()//把迭代器复位，并放在表头

{

current=ourList.getFirst();

previous= null;

}public boolean atEnd()//判断当前节点是否为最后一个链节点

{return (current.next == null);

}public void nextLink()//到下一个链接点

{

previous=current;

current=current.next;

}public Link9 getCurrent()//得到当前链接点的内容

{returncurrent;

}public void insertAfter(long dd)//在当前链接点后插入新的链节点

{

Link9 newLink= newLink9(dd);if(ourList.isEmpty())

{

ourList.setFirst(newLink);

current=newLink;

}else{

newLink.next=current.next;

current.next=newLink;

nextLink();

}

}public void insertBefore(long dd)//在当前链接点前插入新的链节点

{

Link9 newLink= newLink9(dd);if(previous == null)

{

newLink.next=ourList.getFirst();

ourList.setFirst(newLink);

reset();

}else{

newLink.next=previous.next;

previous.next=newLink;

current=newLink;

}

}public long deleteCurrent()//删除当前链节点

{long value =current.dData;if(previous == null)

{

ourList.setFirst(current.next);

reset();

}else{

previous.next=current.next;if(atEnd())

reset();elsecurrent=current.next;

}returnvalue;

}

}public classinterIterator5_9 {/***@paramargs

*@throwsIOException*/

public static void main(String[] args) throwsIOException {//TODO Auto-generated method stub

LinkList9 theList = newLinkList9();

ListIterator iter1=theList.getIterator();longvalue;

iter1.insertAfter(20);

iter1.insertAfter(40);

iter1.insertAfter(80);

iter1.insertBefore(60);while(true)

{

System.out.println("Enter first letter of ");

System.out.print("show,reset,next,get,before,after,delete: ");

System.out.flush();int choice =getChar();switch(choice) {case 's':if(!theList.isEmpty())

theList.dispalyList();elseSystem.out.println("List is empty!");break;case 'r':

iter1.reset();break;case 'n':if(!theList.isEmpty() && !iter1.atEnd())

iter1.nextLink();elseSystem.out.println("can't go to nextLink");break;case 'g':if(!theList.isEmpty())

{

value=iter1.getCurrent().dData;

System.out.println("returned" +value);

}elseSystem.out.println("List is Empty");break;case 'b':

System.out.println("Enter value to insert: ");

System.out.flush();

value=getInt();

iter1.insertBefore(value);break;case 'a':

System.out.println("Enter value to insert: ");

System.out.flush();

value=getInt();

iter1.insertAfter(value);break;case 'd':if(!theList.isEmpty())

{

value=iter1.deleteCurrent();

System.out.println("Deleted" +value);

}elseSystem.out.println("Can't delete");break;default:

System.out.println("Invalid entry");

}

}

}public static String getString() throwsIOException

{

InputStreamReader isr= newInputStreamReader(System.in);

BufferedReader br= newBufferedReader(isr);

String s=br.readLine();returns;

}public static char getChar() throwsIOException

{

String s=getString();return s.charAt(0);

}public static int getInt() throwsIOException

{

String s=getString();returnInteger.parseInt(s);

}

}