找不到符号变量。。。V扩展类中声明的对象

Question

我在学校练习Java，现在有麻烦了。

这是我的图表。java文件：

package graph;

public interface Graph<V>{
    public boolean hasEdge(V one, V two);
    public void addNode(V other);
    public void addEdge(V other);
}

这是我的无向图。java文件：

package graph.undirected;

import graph.*;
import java.util.*;

public class UndirectedGraph<V> implements Graph<V>{

    private HashMap<V,V> neighbourList;
    private TreeMap<V,V> prev;
    private TreeMap<V,Integer> dist;

    public UndirectedGraph(){
        neighbourList = new HashMap<V,V>();
        prev = new TreeMap<V,V>();
        dist = new TreeMap<V,Integer>();
    }

    public boolean hasEdge(V one, V two){
        if(!(this.neighbourList.containsKey(one) && this.neighbourList.containsKey(two))){
            throw new java.util.NoSuchElementException("Nonexistent node.");
        }
        else{
            if( one.neighbourList.containsKey(two) && two.neighbourList.containsKey(one) ){
                return false;
            }
            return true;
        }
    }
    public void addNode(V other){
        if(!(this.neighbourList.containsKey(other))){
            // some code will come here
        }
    }
    public void addEdge(V other){
        if(!(this.neighbourList.containsKey(other))){
            // and some code will come here too
        }
    }
}

我得到了以下错误：

graph\undirected\UndirectedGraph。java:23:错误：找不到符号if（1.neightourlist.containsKey（2）

我被困在这里了。有人能帮我吗？

Answer 1

one和two属于V类型，在您的示例中，它是一个对象。这种类型的V没有邻里关系列表字段，因此无法编写以下内容，因为它无法编译：

if( one.neighbourList.containsKey(two) && two.neighbourList.containsKey(one) ){