Can't find a public symbol variable on one instance of a class (Java)

Question

I am writing a program to calculate the shortest path between two nodes. In my program I have one custom class called NodeList, which contains an ArrayList of strings (representing nodes) along with a distance. I am using Dijkstra's algorithm which involves opening up the shortest edge from each node. So, I use this loop to tabulate the possible routes from a given point:

for ( NodeList ed : edges )
    {
     if (ed.nodeList.get(0).equals(node1))
     {
      routes.add(ed);
     }
    }

This works fine, and appears to load the correct values into the variables (according to the debugger). However, when I try and set a variable to the distance of one of the nodes, I get a message "cannot find symbol variable distance". Here is the code that causes the problem:

int minDistance = routes.get(0).distance;

Is this abnormal or is there something obvious I'm missing?

Answer 1

如果节点列表不使用泛型，则编译器将无法确定您要get()类型get()这意味着它假设它是一个Object ，这意味着它没有distance成员。

Answer 2

get(0) apparently returned an object of class type which doesn't have the particular field.

There are several solutions depending on the root cause of the problem:

• Parameterize the list if possible (eg NodeList<Route> instead of NodeList )
• Cast it to the right type (eg int distance = ((Route) routes.get(0)).distance)
• Make the field public (eg public int distance; )
• Add a getter (eg public int getDistance() { return this.distance; } ) and use it.

Answer 3

Your code doesn't make sense. You say that you have an ArrayList of Strings , but you are looking for a member called 'distance'. String doesn't have a public field called 'distance'.

Most likely you need to declare ArrayList<SomeClassOfYours> to fix this, but I can't tell what from what you posted.