Parsing Double from CSV throws RuntimeException

Question

I am trying to read the data from CSV file. everything works fine but when i try to read the data for longitude and latitude. it gives me an below error message.

 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.yogi.guestlogix/com.example.yogi.guestlogix.MainActivity}: java.lang.NumberFormatException: Invalid double: "EVE" Caused by: java.lang.NumberFormatException: Invalid double: "EVE"**

MainActivity.java

 //Airports data begin InputStream isss = getResources().openRawResource(R.raw.airports); BufferedReader readerss = new BufferedReader( new InputStreamReader(isss, Charset.forName("UTF-8")) ); String liness = ""; //for airports.csv try { readerss.readLine(); while ((liness = readerss.readLine()) != null) { //split by ',' first String[] airport = liness.split(","); //Read the data AirportsData airdata = new AirportsData(); airdata.setAirportname(airport[0]); airdata.setAirportcity(airport[1]); airdata.setAirportcountry(airport[2]); airdata.setAirportIATAcode(airport[3]); //airdata.setAirportlang(Double.parseDouble(airport[4])); //airdata.setAirportlat(Double.parseDouble(airport[5])); AirportsDatas.add(airdata); } } catch (IOException e) { Log.wtf("My Activity", "Reading data file error " + liness, e); e.printStackTrace(); } Log.d("Airline", "name is " + AirportsDatas);

AirportsData.java

public double getAirportlang(double airportlang) { return airportlang; } public void setAirportlang(double airportlang) { this.airportlang = airportlang; } public double getAirportlat( ) { return airportlat; } public void setAirportlat(double airportlat) { this.airportlat = airportlat; } @Override public String toString() { return "AirportsData{" + "airportname='" + airportname + '\'' + ", airportcity='" + airportcity + '\'' + ", airportcountry='" + airportcountry + '\'' + ", airportIATAcode='" + airportIATAcode + '\'' + ", airportlang=" + airportlang + ", airportlat=" + airportlat + '}'; }

**Any solution for this problem would be greatly appreciated....

Is it possible that there is no longitude/latitude set in the database and (for example) airport[4] is "EVE"? If yes, then you need to check for that before using Double.parseDouble(). It cannot parse "" or "EVE"... Why is the String "EVE" returned when you query numeric values? — deHaar
– deHaar, Commented Sep 21, 2018 at 6:42

Maximilian C. · Accepted Answer · 2018-09-21 07:29:28Z

The problem with CSV files is, that users (and other programmers) can pretty much write into the file what they want.

In your case, somebody entered a non-number into a CSV cell where you were expecting a double floating point number. Java correctly complains that this cannot be parsed to double. You have two approaches, to treat such situations:

A) Design by Contract

First, you could resolve that by relying on design by contract. You could have a parseLat method:

public Double parseLat(String[] csvRow) { final String lat= csvRow[4]; assertIsNumeric(lat); } private void assertIsNumeric(String lat) { if(!isNumeric(lat)) { throw new IllegalArgumentException("Lattitude '" + lat + "' is not numeric"); } }

There are countless options to implement an isNumeric method, some are discussed here. This will still stop the execution, but it will give a clearer message to users.

B) Defensive Design

A second option, is to provide a parseLAttitude method, that replaces non numeric value with null:

public Double parseLattitude(String[] csvRow) { final String lattitude = csvRow[4]; if(!isNumeric(lattitude)) { System.out.println("Could not parse lattitude '" + lat + "'"); return null; } return Double.parseDouble(lat); }

Stephan Hogenboom · Accepted Answer · 2018-09-21 07:14:00Z

I think the problem is that airport[4] & airport[5] might not be the lon and lat of the airport. If these field contain alpha characters [a-z] you will get an numberFormatException. Can you add the the output when you print airport like:

System.out.println(Arrays.asList(airport));

to the question? Than we will be better able to help you

I think this is a helpful hint, but should be a comment instead of an answer :)

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