好久没有看数据结构相关内容，忽然面试官让写判断链表是否有环，竟然写了半天写不出来，汗~

知道自己有多渣，就好好学习吧

接下来开始写判断链表是否有环的方法吧

1.首先定一个结点类Node

package com.example.demo;public class Node
    
      {    private T val;    private Node
     
       next;    public Node(T object) {        this.val=object;    }    public void Node(T val) {        this.val = val;    }    public void setVal(T val){        this.val=val;    }    public T getVal(){        return this.val;    }    public Node
      
        getNext(){        return this.next;    }    public void setNext(Node
       
         node) {        this.next = node;    }    }
       
      
     
    

2.然后链表类

package com.example.demo;import java.util.List;public class LinkList {    private Node root;    private List
    
      list;    public LinkList() {    }    public Node getRoot(){        return this.root;    }    public List
     
       getList() {        return list;    }    public void setList(List
      
        list) {        this.list = list;    }    public void setRoot(Node node) {        this.root = node;    }    public boolean isExistRound(Node root){        if(root==null){            return false;        }        if(root.getNext()==null){            return false;        }        Node p=root;        Node q=root.getNext();        while(q!=null){            if(p==q){                return true;            }            q=q.getNext();        }        return false;    }}
      
     
    

3.然后是单元测试

package com.example.demo;import org.junit.Assert;import org.junit.Test;import java.util.ArrayList;import java.util.List;public class LinkListTest {    @Test    public void should_return_true_when_link_is_round() {        String str = "1-2-3-4-5-6";        LinkList roundlinkList = createRoundLinkList(str);        Assert.assertEquals(true, roundlinkList.isExistRound(roundlinkList.getRoot()));        LinkList notRoundLinkList=createNotRoundLinkList(str);        Assert.assertEquals(false, notRoundLinkList.isExistRound(notRoundLinkList.getRoot()));    }    @Test    public void should_return_linked_list_value() {        String str = "1-2-3-4-5";        LinkList linkList = createNotRoundLinkList(str);        Node node = linkList.getRoot();        while (node != null) {            System.out.println(node.getVal() + " ");            node = node.getNext();        }    }    public LinkList createRoundLinkList(String str) {        LinkList linkList = createNotRoundLinkList(str);        List
    
      nodeList = linkList.getList();        nodeList.get(nodeList.size()-1).setNext(nodeList.get(0));        linkList.setList(nodeList);        return linkList;    }    public LinkList createNotRoundLinkList(String str) {        LinkList linkList = new LinkList();        List
     
       nodeList = new ArrayList<>();        Object[] objects = str.split("-");        for (int i = 0; i < objects.length; i++) {            nodeList.add(new Node<>(objects[i]));        }        linkList.setRoot(nodeList.get(0));        for (int j = 0; j < nodeList.size() - 1; j++) {            nodeList.get(j).setNext(nodeList.get(j + 1));        }        linkList.setList(nodeList);        return linkList;    }}