Solved

removing members from an ArrayList

Posted on 2007-04-05
6
212 Views
Last Modified: 2012-05-05
i am adding an object "pnew" to a queue (which i am implementing as an arrayList--same thing right?) after I add it i need to back up a step so I have a "remove" method which takes off the last element in "pnew".  The problem is that when I remove the member from "pnew", it also removes it from the queue.  The queue is an ArrayList of paths, pnew is an ArrayList of integers

path pnew = new path(start);
ArrayList<path> queue = new ArrayList<path>();

queue.add(pnew);
pnew.remove();
0
Comment
Question by:jpking72
  • 3
  • 3
6 Comments
 
LVL 30

Expert Comment

by:Mayank S
ID: 18860643
>> which i am implementing as an arrayList--same thing right

You mean the ArrayList implements a queue? It can....

Though it looks like you have:

/* Queue --> */ path pnew = new path(start);
/* ArrayList --> */ ArrayList<path> queue = new ArrayList<path>(); // also named as 'queue' ?

>> pnew.remove();

We need to know what is the implementation of the path class and what it does.
0
 

Author Comment

by:jpking72
ID: 18861378
====================================================

        int source = this.findNode(a);
        int sink = this.findNode(b);
        curr.add(source);
        path p = new path(curr);
        queue.add(p);
       
       
       
        for (int row = 0; row < nodes.length; row++) {
            path pnew = queue.remove(0);
            for (int col = 0; col < nodes.length;  col++) {
                if (matrixCap[row][col] != 0) {
                    pnew.add(col);
                    if (pnew.contains(sink))
                        System.out.println(queue.toString());
                    queue.add(pnew);
                    pnew.remove();
                }
        }
           
       
    }
========================================
class path
========================================
public class path {
   
    private ArrayList<Integer> in = new ArrayList<Integer>();
   
    /** Creates a new instance of path */
    public path(ArrayList<Integer> i) {
       
        for (int j = 0; j < i.size(); j ++) {
            in.add(j, i.get(j));
        }
       
    }
   
    public ArrayList<Integer> add(Integer i) {
       
        in.add(i);
        return in;
    }
   
    public ArrayList<Integer> remove() {
       
        if (in.size() >0){
        in.remove(in.size()-1);
        return in;}
       
        else return in;
       
    }
   
    public boolean contains(int sink) {
        for (int i = 0; i < in.size(); i++) {
            if (in.get(i).equals(sink))
                return true;
        }
        return false;
    }
   
    public String toString() {
        StringBuilder out = new StringBuilder();
        out.append("found path: ");
       
        for (int i = 0; i < in.size(); i++)  {
            out.append(in.get(i));
            out.append(" ");
        }    
            return out.toString();
       
   
}
}
0
 
LVL 30

Accepted Solution

by:
Mayank S earned 500 total points
ID: 18866335
'queue' is an array list of path, so there is not a direct relationship between path and 'queue'.
0
Industry Leaders: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

 

Author Comment

by:jpking72
ID: 18867304
i don't understand...i rewrote the code and still the same problem:
when I update current[i], queue also changes the previous entry in the ArrayList.  I want it to add another distinct array to the end of the ArrayList every time.

ArrayList<int[]> queue = new ArrayList<int[]>();
int[] current = new int[10];

for (col = 0; col<nodes.length; col++) {
current[i] = col;
queue.add(current)
}
0
 

Author Comment

by:jpking72
ID: 18868345
hello?
0
 
LVL 30

Expert Comment

by:Mayank S
ID: 18868854
If path holds Integers, maybe even the array list should be of Integers

ArrayList <Integer> queue = new ArrayList <Integer> () ;

>> hello?

Be patient - I come here in my free time and our time zones could also be different. Any reason for the C  grade?
0

Featured Post

On Demand Webinar - Networking for the Cloud Era

This webinar discusses:
-Common barriers companies experience when moving to the cloud
-How SD-WAN changes the way we look at networks
-Best practices customers should employ moving forward with cloud migration
-What happens behind the scenes of SteelConnect’s one-click button

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
tomcat administrtor 12 68
Selenium docs api java index 3 64
learn programming 8 66
Java array sort 10 29
Java had always been an easily readable and understandable language.  Some relatively recent changes in the language seem to be changing this pretty fast, and anyone that had not seen any Java code for the last 5 years will possibly have issues unde…
This was posted to the Netbeans forum a Feb, 2010 and I also sent it to Verisign. Who didn't help much in my struggles to get my application signed. ------------------------- Start The idea here is to target your cell phones with the correct…
Viewers will learn one way to get user input in Java. Introduce the Scanner object: Declare the variable that stores the user input: An example prompting the user for input: Methods you need to invoke in order to properly get  user input:
This tutorial covers a step-by-step guide to install VisualVM launcher in eclipse.

735 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question