Java LinkedList 数组引用

Question

所以我有一个简单的程序，它创建一个给定大小 n 的 LinkedList 数组，列表中的每个值代表一个新的单独的 LinkedList 数据结构。

public class Graph {

public final LinkedList[] graph;

public Graph(int n){
    graph = new LinkedList[n];  

    for (int i=0; i<n; i++){
        graph[i] = new LinkedList();
    }

}

public void addEdge(int x, int y){

    graph[x].addFirst(y);
    graph[y].addFirst(x);

}

但是，由于某种原因，当我使用两个 int 值调用 addEdge() 方法时，而不是将它们添加到 graph 中名为 LinkedList 的特定位置[]，它将它们添加到 graph[] 中的每个 LinkedList 中。

这里有什么问题吗？

编辑:*

public void addEdge(int x, int y){

    graph[x].addFirst(y);
    graph[y].addFirst(x);

    for (int i=0; i<graph.length; i++){
        Node tmp = graph[i].first;

        System.out.println(i + ":");

        while (tmp != null){
            System.out.print(tmp.name + " ");

            tmp = tmp.Rnext;
        }
        System.out.println();
    }
    System.out.println();

}


public class Test {

public static void main(String[] args) {


    Graph myGraph1 = new Graph(8);
    myGraph1.addEdge(1, 2);
    myGraph1.addEdge(1, 7);
    myGraph1.addEdge(1, 4);
    myGraph1.addEdge(2, 5);
    myGraph1.addEdge(2, 6);
    myGraph1.addEdge(6, 3);
    myGraph1.addEdge(3, 8);
    myGraph1.addEdge(5, 7); 
    }
}

Here is the output of graph:
0:
1 2 
1:
1 2 
2:
1 2 
3:
1 2 
4:
1 2 
5:
1 2 
6:
1 2 
7:
1 2 

0:
1 7 1 2 
1:
1 7 1 2 
2:
1 7 1 2 
3:
1 7 1 2 
4:
1 7 1 2 
5:
1 7 1 2 
6:
1 7 1 2 
7:
1 7 1 2 

0:
1 4 1 7 1 2 
1:
1 4 1 7 1 2 
2:
1 4 1 7 1 2 
3:
1 4 1 7 1 2 
4:
1 4 1 7 1 2 
5:
1 4 1 7 1 2 
6:
1 4 1 7 1 2 
7:
1 4 1 7 1 2 

0:
2 5 1 4 1 7 1 2 
1:
2 5 1 4 1 7 1 2 
2:
2 5 1 4 1 7 1 2 
3:
2 5 1 4 1 7 1 2 
4:
2 5 1 4 1 7 1 2 
5:
2 5 1 4 1 7 1 2   
6:
2 5 1 4 1 7 1 2 
7:
2 5 1 4 1 7 1 2 

0:
2 6 2 5 1 4 1 7 1 2 
1:
2 6 2 5 1 4 1 7 1 2 
2:
2 6 2 5 1 4 1 7 1 2 
3:
2 6 2 5 1 4 1 7 1 2 
4:
2 6 2 5 1 4 1 7 1 2 
5:
2 6 2 5 1 4 1 7 1 2 
6:
2 6 2 5 1 4 1 7 1 2 
7:
2 6 2 5 1 4 1 7 1 2 

0:
6 3 2 6 2 5 1 4 1 7 1 2 
1:
6 3 2 6 2 5 1 4 1 7 1 2 
2:
6 3 2 6 2 5 1 4 1 7 1 2 
3:
6 3 2 6 2 5 1 4 1 7 1 2 
4:
6 3 2 6 2 5 1 4 1 7 1 2 
5:
6 3 2 6 2 5 1 4 1 7 1 2 
6:
6 3 2 6 2 5 1 4 1 7 1 2 
7:
6 3 2 6 2 5 1 4 1 7 1 2 

这是我正在使用的 LinkedList 和 Node 类:

import java.util.NoSuchElementException;

public class LinkedList {

public static Node first;

    public LinkedList(){ 
    first = null;

    } 

    // Returns true if the list is empty 
    public boolean isEmpty(){ 
    return first == null; 
    } 

    // Inserts a new node at the beginning of this list. 
    public void addFirst(int name){ 

    first = new Node(name, first);
    }


    public boolean findData(int d){
    if(first == null) throw new NoSuchElementException();
    Node tmp = first;

    while (tmp != null) {

        if (tmp.name == d) return true;
        tmp = tmp.Rnext;
    } return false;
}
}


    public class Node { 

    public int name;
    public Node Rnext;

    public Node(){ 
    name = 0;
    Rnext = null; 
    } 

    public Node(int n, Node r){ 
    this.name = n;
    this.Rnext = r;
} 

}

Answer 1

public static Node first;

这就是问题所在。您创建的每个 LinkedList 都共享相同的 Node，因此它们实际上都是相同的列表。

不要使用static作为实例变量。