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Thread: help with using Java ArrayList

  1. #1
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    Default help with using Java ArrayList

    I'm learning to build an directed graph data structure using adjacency lists, so I thought I'd use LinkedLists to ensure efficient linked list used and I wanted to use an array of Linked list, but I had trouble so I decided to use ArrayList of LinkedList of type Integer, but compiler complains about generics.

    The problem I have is having a wrapper that adds a new vertex to the current end of a LL (so it's a wrapper for addLast(Elem e) which is really a LinkedList method)

    import java.util.*;
    import java.lang.*;
     
    class Graph//implemented via adjacency lists
    {
    	public Graph(int size)
    	{
    		this.size = size;
    		l = new LinkedList(size);
    	}
     
    	public void add_to_end(Integer i)//problem here...
    	{
    		this.l.add(i);//PROBLEM: this.l is a Linked List data member but compiler complains...
    	}
     
     
    	public void print(){return;}//prints each index (so each adjacent node for a given node)
     
     
    	public void dft(){return;}//Depth-first traversal of current graph
     
     
    	public void bft(){return;}//breadth-first " "
     
     
    	public int get_size(){return this.size;}
     
    	private int size;//number of vertices
    	private ArrayList l;
    }
     
    public class Graphs_runner
    {	
    	public static void main(String[] args)
    	{
    	}
    }


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    Default Re: help with using Java ArrayList

    compiler complains about generics.
    Please post the full text of the error message.

    problem I have is having a wrapper that adds a new vertex to the current end of a LL
    Can you explain what you mean? Are you asking how to write a method?
    If you don't understand my answer, don't ignore it, ask a question.

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