Solved

removing members from an ArrayList

Posted on 2007-04-05
6
209 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
Ransomware: The New Cyber Threat & How to Stop It

This infographic explains ransomware, type of malware that blocks access to your files or your systems and holds them hostage until a ransom is paid. It also examines the different types of ransomware and explains what you can do to thwart this sinister online threat.  

 

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

Ransomware-A Revenue Bonanza for Service Providers

Ransomware – malware that gets on your customers’ computers, encrypts their data, and extorts a hefty ransom for the decryption keys – is a surging new threat.  The purpose of this eBook is to educate the reader about ransomware attacks.

Question has a verified solution.

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

Suggested Solutions

Title # Comments Views Activity
How to get all the API from website? 11 91
GUI builder for Eclipse? 8 36
VB Script to add site to Java Exception List 4 78
login form jsp example 2 26
Go is an acronym of golang, is a programming language developed Google in 2007. Go is a new language that is mostly in the C family, with significant input from Pascal/Modula/Oberon family. Hence Go arisen as low-level language with fast compilation…
Basic understanding on "OO- Object Orientation" is needed for designing a logical solution to solve a problem. Basic OOAD is a prerequisite for a coder to ensure that they follow the basic design of OO. This would help developers to understand the b…
Viewers will learn about arithmetic and Boolean expressions in Java and the logical operators used to create Boolean expressions. We will cover the symbols used for arithmetic expressions and define each logical operator and how to use them in Boole…
Viewers will learn about basic arrays, how to declare them, and how to use them. Introduction and definition: Declare an array and cover the syntax of declaring them: Initialize every index in the created array: Example/Features of a basic arr…

809 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