For Loop doesnt add point to an array

Question

I have the following for loop which looks through a string ArrayList of results, each item in the string is seperated by "::":

ArrayList<String> resultsArray = MyClass.results;
        Integer numPoints = resultsArray.size();

        for (int i =0;i<numPoints;i++){
            String[] pointDetails = resultsArray.get(i).split("::");
            String pointName = pointDetails[0];
            String pointDescription = pointDetails[1];
            String coordinates = pointDetails[2];

        //Turn coordinates into geopoints
            String coord[] = coords.split(",");
            Integer  lng= (int) (Double.valueOf(coord[0]) * 1000000);
            Integer lat = (int)(Double.valueOf(coord[1])*1000000);
            GeoPoint gPoint = new GeoPoint(lng,lat);


         arrayPointName = new ArrayList <String>();
         arrayPointDescription = new ArrayList <String>();
         arrayPointCoords=new ArrayList<GeoPoint>();
         arrayPointName.add(pointName);
         arrayPointDescription.add(pointDescription);
     arrayPointCoords.add(gPoint);
          }

I know I have 20 points in the initial string ArrayList and have printed out its size to check this. However, when I print out the new arraylists, such as arrayPointName, they only contain one point. Any idea on why this is?

You're creating a new instance of arrayPointName within your for loop each time you iterate, meaning you will only ever have a single item in it. — Aaron McIver
– Aaron McIver, Commented Apr 19, 2013 at 15:01
The best way to solve your problem is to trace your code using your IDE's debug tools, it will take you a couple of minutes to locate the problem. — Egor
– Egor, Commented Apr 19, 2013 at 15:01
Because you are re-creating arrayPointName inside the for loop — Robin Chander
– Robin Chander, Commented Apr 19, 2013 at 15:01

Jon Skeet · Accepted Answer · 2013-04-19 15:01:24Z

7

Look at this code:

arrayPointName = new ArrayList <String>();
arrayPointDescription = new ArrayList <String>();
arrayPointCoords=new ArrayList<GeoPoint>();

Those three statements - assigning new, empty ArrayList references to your variables - are being executed on every iteration of your loop.

They should come before your loop instead: you only want to initialize the variables once (creating the three lists) and then add a new item on each iteration.

As a side note, populating multiple collections like this is normally a bad idea. It's usually better to create a single type which encapsulates the related data (name, description, coordinates in this case) and then create a single collection of items of that type. That's usually a lot easier to work with.

answered Apr 19, 2013 at 15:01

Jon Skeet

1.5m893 gold badges9.3k silver badges9.3k bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Aydroid · Accepted Answer · 2013-04-19 15:12:06Z

0

you used coords as an ArrayList Without initiate it .Also you initiate for each iteration arrayPointName, arrayPointDescription and arrayPointCoords that's why they lost the value created in the previous iteration. they should be initiate juste one time before starting the loop

it will be easy to help you if you give us a sample of resultsArray strring.

answered Apr 19, 2013 at 15:12

Aydroid

811 silver badge4 bronze badges

Collectives™ on Stack Overflow

For Loop doesnt add point to an array

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related