数据结构（java）---MyLinkedList

来源：互联网发布：淘宝培训kehuda 编辑：程序博客网时间：2024/05/21 10:33
看着书自己写了一遍linkedlist，以及其中的迭代器的实现
import java.util.ConcurrentModificationException;import java.util.Iterator;import java.util.NoSuchElementException;public class MyLinkedList<T> implements Iterable<T> {    //声明必要的变量    private int modCount = 0;//链表自从被构建以来，对链表所做的改变的次数，用于检测迭代器中的删除操作是否可以执行    private int theSize;//链表的大小    private Node<T> beginMarker;//链表的头指针    private Node<T> endMarker;//链表的尾指针    private static class Node<T>    {        public Node(T d, Node<T> p,Node<T> n)        {data = d;prev = p;next = n;}        public T data;        public Node<T> prev;//由于java Collection中的LinkedList采用的是双链表，因此每个节点需要有前驱和后继指针        public Node<T> next;    }//对于每一个节点采用静态内部类    public MyLinkedList(){  doClear();}    public void clear(){    doClear();}    public int size(){return theSize;}    @Override    public String toString() {//重写toStirng方法用来遍历链表        // TODO Auto-generated method stub        Node<T> p = beginMarker.next;        String str = "";        for(int i = 0 ; i < size() ; i++)            {            str+=p.data.toString();            str+=";";            p = p.next;}        return str;    }    public boolean isEmpty(){return size()==0;}    public boolean add(T x){add(size(),x);return true;}//在链表的尾部插入节点    public void add(int idx, T x){addBefore(getNode(idx,0,size()),x);}//在指定的索引处添加节点    public T get(int idx){ return getNode(idx).data;}    public T set(int idx, T newValue){T oldValue = getNode(idx).data; getNode(idx).data = newValue; return oldValue;}    public T remove(int idx){return remove(getNode(idx));}    private T remove(Node<T> p){        p.prev.next = p.next;        p.next.prev = p.prev;        theSize--;        modCount++;        return p.data;    }    private void addBefore(Node<T> p , T x){        Node<T> newNode = new Node(x,p.prev,p);        newNode.prev.next = newNode;        newNode.next.prev = newNode;        theSize++;        modCount++;    }    private Node<T> getNode(int idx){ return getNode(idx,0,size()-1);}    private Node<T> getNode(int idx,int lower, int upper){        Node<T> p ;        if(idx > upper ||idx < lower)            throw new IndexOutOfBoundsException();            //如果idx的值在前半部分，就从前向后遍历，如果在后半部分就从后向前遍历        if(idx < size()/2)        {            p = beginMarker.next;            for(int i = 0 ; i < idx ; i++)                p = p.next;        }        else{            p = endMarker;                        //p = endMarker.prev;            for(int i = size(); i > idx ; i--)    //for(int i = size()-1 ; i >idx ; i--)                p= p.prev;                        // p = p.prev;        }        return p;    }    private void doClear()    {        beginMarker = new Node<T>(null,null,null);        endMarker = new Node<T>(null,beginMarker,null);        beginMarker.next = endMarker;        theSize = 0;        modCount++;    }    @Override    //通过调用iterator函数生成当前这个链表的迭代器    public Iterator<T> iterator() { return new LinkedListIterator();}    //用内部类继承接口实现迭代器    private class LinkedListIterator implements Iterator{        private Node<T> current = beginMarker.next;//用来表示迭代器当前的位置        private int expectedModCount = modCount;//用来检测在迭代器进行remove，next之前有没有执行链表的其他的操作        private boolean okToRemove = false;        @Override        public boolean hasNext() {            // TODO Auto-generated method stub            return current!=endMarker;        }        @Override        public Object next() {            // TODO Auto-generated method stub            if(modCount != expectedModCount)                throw new ConcurrentModificationException();//说明在迭代器进行遍历之前对链表进行了操作，因此不能在迭代器中进行查找下一项和删除的操作            if(!hasNext())                throw new NoSuchElementException();            T nextItem = current.data;            current = current.next;            okToRemove = true;//表示当前节点的状态是可以删除的            return nextItem;        }        @Override        public void remove() {            // TODO Auto-generated method stub        if(modCount != expectedModCount)            throw new ConcurrentModificationException();        if(!okToRemove)            throw new IllegalStateException();        MyLinkedList.this.remove(current.prev);        expectedModCount++;//同步expectedModCount和modCount        okToRemove = false;//当前的项已经删除因此不可再进行删除，把okToRemove改为false        }    }    public static void main(String[] args) {         MyLinkedList<Integer> list = new MyLinkedList<Integer>();         list.add(10);         list.add(20);         list.add(30);         System.out.println(list);//输出结果10;20;30    }}
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