从列表字符串存储到另一个数组列表

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().

Answer 1

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!

Answer 2

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

Answer 3

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)
    }

Answer 4

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]));

Answer 5

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());

Answer 6

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));
    }

Answer 7

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

Answer 8

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));
        }
     }
}