Java instance variable array size based on another instance variable-CodePudding

I am trying to make a graph class that has an array as an instance variable, but the size of this array is dependent on another instance variable which will be intialized in the constructor. Here's a Simple example:

public class Graph {
//Number of Vertices and Edges:
private int V;
private int E;
//Visited/Unvisited list:
private int[] visitedList = new int[V];

//Constructor:
public Graph(int V){
        this.V = V;
        this.E = 0;
        for (int i = 0; i < V; i  ) { //Initialize all vertices as 0
            visitedList[i] = 0;
        }
}

As you can see, the size of the visitedList will be dependent on the variable V which we initialize via the constructor. However, I get an error inside the constructor when I try to initialize the visitedList after getting the value of V. Is there a proper way to intialize the array visitedList such that the size follows V and I can intiailize all the elements to 0? Or do I need to do it some other way outside the constructor with another method that perhaps intializes the visitedList? Any help is welcome, thank you!

CodePudding user response：

You currently construct the array before the other statements in your constructor run. You need to change that

private int[] visitedList; // V is 0 at this point.

//Constructor:
public Graph(int V){
        this.V = V;
        this.E = 0;
        this.visitedList = new int[V];
        // default initial value in an int[] **is** zero.
}