store from list string to another array list

Question

I have a txt file like this which contains longitude and latitude coords:

120.12    22.233
100    23.12
98     19.12

If I want to read the file, I am doing:

List<String> lines = Files.readAllLines(Paths.get(fileName));
System.out.println("LINE: " + lines.get(0));

and it gives me : 120 22

I have a class that reads latitude and longitude:

public class GisPoints {

    private double lat;
    private double lon;

    public GisPoints() {
    }

    public GisPoints(double lat, double lon) {
       super();
       this.lat = lat;
       this.lon = lon;
    }

    //Getters and Setters
}

I want to store all the values from the txt file into an List<GisPoints>.

So, I want a function in order to load file:

public static List<GisPoints> loadData(String fileName) throws IOException {

      List<String> lines = Files.readAllLines(Paths.get(fileName));

      List<GisPoints> points = new ArrayList<GisPoints>();

      //for (int i = 0; i < lines.size(); i++) {

     // }

      return points;

  }

As I said, right now I am just reading every line, for example lines[0] = 120 22

I want to store lines[0] longitude into points[0].setLon(), lines[0] latitude into points[0].setLat().

since your file contains only ints, you can use nextInt method in Scanner class — Ahmad Al-Sanie
– Ahmad Al-Sanie, Commented Jul 26, 2017 at 9:06
@AhmadAlsanie Why OP need scanner as he already read the file and got lines ? I didn't understand what you mean. — Suresh Atta
– Suresh Atta, Commented Jul 26, 2017 at 9:09

Yannick · Accepted Answer · 2017-07-26 09:17:06Z

2

This is an easy solution with String.split()

private GisPoints createGisPointsObjectFromLine(String p_line)
{
    String[] split = p_line.trim().split(" ");
    double lat = Double.parseDouble(split[0]);
    double lon = Double.parseDouble(split[split.length - 1]);
    return GisPoints(lat, lon);
}

You can call this method from your loadData() method. I hope this solution is helpful. Good luck!

answered Jul 26, 2017 at 9:17

Yannick

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Comments

score 1 · Accepted Answer · 2017-07-26 09:24:30Z

1

It would look like this:

    for (int i = 0; i < lines.size(); i++)
    {
        String line = lines.get(i);

        String[] values = line.split("\\s+");

        double lat = Double.parseDouble(values[0]);
        double lon = Double.parseDouble(values[1]);

        points.add(new GisPoints(lat, lon));
    }

edited Jul 26, 2017 at 9:24

answered Jul 26, 2017 at 9:16

user6872100

4 Comments

George Over a year ago

It shows: java.lang.NumberFormatException: For input string: "-117.1".I am trying to use -117.1 32.533

George Over a year ago

Now, if I print points, it gives me the package name mylib.gispoint.GisPoints@262a8f13, mylib.gispoints.GisPoints@22150f0e,....

XtremeBaumer Over a year ago

@George you have to override the toString() method in your GisPoints class

user6872100 Over a year ago

@George Or get the values through the getter-methods in GisPoint and print it then.

Antony Dao · Accepted Answer · 2017-07-26 09:10:19Z

1

I think split can solve your problem:

String arr[] = lines[i].split("\\s+");
GisPoints p = new GisPoints(Double.parseDouble(arr[0]), Double.parseDouble(arr[1]));

edited Jul 26, 2017 at 9:10

answered Jul 26, 2017 at 9:09

Antony Dao

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1 Comment

Suresh Atta Over a year ago

arr[0] is String. Not double.

Suresh Atta · Accepted Answer · 2017-07-26 09:11:15Z

1

I want to store lines[0] longitude into points[0].setLon(), lines[0] latitude into points[0].setLat().

You don't need setters right away. You have a good constructor to receive both of them already.

Just create an object after splitting like into two parts.

 for (int i = 0; i < lines.size(); i++) { 
      String[] latlang = lines.get(i).split("\\s+");
      GisPoints g = new GisPoints(Double.parseDouble(latlang[0].trim()),Double.parseDouble(latlang[1].trim()));
      points.add(g)
    }

edited Jul 26, 2017 at 9:11

answered Jul 26, 2017 at 9:08

Suresh Atta

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2 Comments

SomeJavaGuy Over a year ago

you forgot the splitting i guess :)

Suresh Atta Over a year ago

@SomeJavaGuy Oh no. You saved me :D

XtremeBaumer · Accepted Answer · 2017-07-26 09:13:23Z

1

for (String str : lines) {
    String[] helpArray = str.split("\\s+"); // or whatever is betweeen
                                            // the two numbers
    points.add(new GisPoints(Double.valueOf(helpArray[0].trim()), Double.valueOf(helpArray[1].trim())));
}

this should work as you need it. only works as long as there are only numbers in the file. you can report back if you need further help

edited Jul 26, 2017 at 9:13

answered Jul 26, 2017 at 9:08

XtremeBaumer

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Comments

Lino · Accepted Answer · 2017-07-26 09:39:11Z

1

You might want to do it with java8-streams:

 List<GisPoint> points = lines.stream()
        .map(s -> s.split("\\s+"))
        .map(array -> Arrays.stream(array)
            .map(String::trim)
            .filter(s -> !s.isEmpty())
            .mapToDouble(Double::parseDouble)
            .toArray()
        )
        .map(array -> new GisPoint(array[0], array[1]))
        .collect(Collectors.toList());

edited Jul 26, 2017 at 9:39

answered Jul 26, 2017 at 9:13

Lino

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8 Comments

XtremeBaumer Over a year ago

you should .trim() the array values

Lino Over a year ago

@XtremeBaumer what about now?

George Over a year ago

@Lino:It shows java.lang.NumberFormatException: For input string: "-117.1 32.5333333333333", if I use these numbers in the file

George Over a year ago

@Lino:yes, i have

XtremeBaumer Over a year ago

you have 1 string with 2 numbers which can never be converted. try splitting with \\s+

|

Robert · Accepted Answer · 2017-07-26 09:05:20Z

0

Take a look at the class Scanner; Scanner has a lot of useful tools for reading and parsing strings.

answered Jul 26, 2017 at 9:05

Robert

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3 Comments

Aaron Over a year ago

This is a good suggestion, but not a complete answer. This would be best as a comment (of course if you intend to improve it that's alright I guess)

Akshay Over a year ago

You can add some code snippet useful to OP ..else it should be a comment

Robert Over a year ago

I must have 50 reputation to comment on questions, which i don't. This is an assignment i think he or she could figure out by himself and thereby i didn't elaborate more, merely pointed him or her in the right direction. Rest assured, if i had 50 rep this would have been simply a comment :-)

Cylexx · Accepted Answer · 2017-07-26 09:15:36Z

0

Take a look with regex :

import java.util.regex.*;

public class HelloWorld{

     public static void main(String []args){
        String line = "98 19";
        Pattern pattern = Pattern.compile("^(\\d+)\\s*(\\d+)$");
        Matcher matcher = pattern.matcher(line);
        while (matcher.find()) {
            System.out.println("group 1: " + matcher.group(1));
            System.out.println("group 2: " + matcher.group(2));
        }
     }
}

answered Jul 26, 2017 at 9:15

Cylexx

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