how to parse data from a csv file into a container and search for 1 value and retrieve the rest of the values on its line in java

Question

i am trying to read comma separated values from a text file which contains a postcode, latitude and longitude on each line and i want to parse this data and then access it when a user inputs a postcode to then find the lat and long on its corresponding line, which then the program takes the lat and long and finds the location on a map using the google maps api, however im having trouble.

this is where i read the file

    public void readFromFile() {

    BufferedReader read = null;
    String line;
    String fileName = "";
    String seperator = ",";


    try {

        FileInputStream fstream = new FileInputStream("test.txt");
        read  = new BufferedReader(new InputStreamReader(fstream));
        //read = new BufferedReader(new FileReader(fileName));

        while ((line = read.readLine()) != null) {
            postcodeCSV = line.split(seperator);
             postcode = postcodeCSV[0] ;


            line = read.readLine();
        }

    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        try {
            if (read != null) read.close();
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }
}
}

This is my main file

  public String postcode ;
  public float latitude ;
  public float longitude ;

public String[] postcodeCSV;

EditText POSTCODE_et;
ImageButton FIND_ib;

private LatLng ADDRESS = new LatLng(latitude, longitude);
private GoogleMap MAP_GM;


@Override
protected void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_address);

    POSTCODE_et = (EditText) findViewById(R.id.postcode_et);
    FIND_ib = (ImageButton) findViewById(R.id.find_ib);
    MAP_GM = ((MapFragment) getFragmentManager().findFragmentById(R.id.map_gm)).getMap();

    readFromFile();


    FIND_ib.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            for (String s : postcodeCSV) {
                String Postcode_getter = POSTCODE_et.getText().toString();
                if (s == Postcode_getter) {
                    latitude = Float.parseFloat(postcodeCSV[1]);//postcodeCSV[1];
                    longitude = Float.parseFloat(postcodeCSV[2]);


                }

                CameraUpdate updateMap = CameraUpdateFactory.newLatLng(ADDRESS);
                MAP_GM.animateCamera(updateMap);
            }

        }

    });



}

Answer 1

I think what you are looking for is a

Map<String, LatLon> postCodeMap = new HashMap<>();

Where the Key is your postcode as a String and Value is a custom class LatLon as shown below:

public class LatLon{
   double latitude;
   double longitude;

   //getter & setters
   //constructor
}

To put a new Value

postCodeMap.put("55555", new LatLon(92.00,-32.75))

To Look Up a new Value:

LatLon latlon = postCodeMap.get("55555");

Answer 2

I think your problem stems from you overwriting the postcode and postcodeCSV for every other line. The every other line part comes from you doing while(line = read.readLine()) and then 5 lines later calling line = read.readLine() again.

Here is what I would do:
A) Create a class called PostOffice with code, lat and long as the fields.

B) remove the second readLine()

C) For each line create a new postOffice

D) Add each new postOffice to a List of postOffices (which should be a field)

F) In your onClick, iterate through the postOffices and check for the user entered value such as

for(PostOffice po : postOffices)
{
  if(po.code == POSTCODE_et.getText().toString())
  {
    latitude = po.lat;
    longitude = po.lon;
  }
}