Thread: Creating ArrayLists

Hi, I am creating a simple program using Kruskals Algorithm

I am stuck on creating almost like a structure to hold the data for the algorithm.

For example, I need an arraylist of:

edges which contains
{
int from;
int to;
int weight;
}

I have tried many ways but cannot do it. I need to be able to add data like

e.g. if i have an arraylist called myEdges
i want to be able to do myEdges.add and be able to add a value for each of the elements inside the edge type.

I will later need to sort the data by the weight.

this is what i have done so far

public class Edge 
{
	public int from;
	public int to;
	public int weight;
 
	public Edge(int from, int to, int cost) 
	{
	this.from = from;
	this.to = to;
	this.weight = cost;
	}
}
	   ArrayList<Edge> myEdges = new ArrayList<Edge>();

but i am not sure how to add data to it.

thank you.

Sorry could you explain further i am new to java.

Hi, would i need to do something like this

Edge myEdges;

ArrayList<Edge> myEdges = new ArrayList<Edge>();

It said duplicate name myEdges

public class Edge
{
public int from;
public int to;
public int cost;
public Edge myEdges;

public Edge(int from, int to, int cost)
{
this.from = from;
this.to = to;
this.cost = cost;
}


Edge Edge1 = new Edge(1, 2, 3 );



ArrayList<Edge> edgeList = new ArrayList<Edge>();

when i type edgeList.
no options come up like add etc

 
import java.util.ArrayList;
 
public class Edge 
{
	static ArrayList<Edge> edgeList = new ArrayList<Edge>(); 
 
	public int from;
	public int to;
	public int cost;
	public Edge myEdges;
 
	public Edge(int from, int to, int cost) 
	{
	this.from = from;
	this.to = to;
	this.cost = cost;
	}
 
 
public Edge Edge1 = new Edge(1, 2, 3);
 
 
	public void Data()
	{
 
	edgeList.add(0, Edge1);
	edgeList.add(1, Edge1);
 
	}
 
 
 
		public static void main(String[] args)
		{
			System.out.print(edgeList.size());
 
		}
 
}

i am printing the arraylist to see if the elements have been added but the arraylist still has a size of 0?

Hi, thanks for your help, I got it working.

Thanks once again.

You definitely have to read a tutorial on the Java Collections Framework to help you understand Lists implementations. After that, you will know why while instantiating an object, you do not need to precede it with the public access keyword as above. Make it easier to understand by separating the two files and use the main method to instantiate the ArrayList class and then add whatever you wanted to. Also, read the Java API Docs for JCF methods.

Hi, thanks everyone for the help but dont worry, I've already done it.

Many thanks.