How return a multidimensional arrayList in java?

Question

I want to create a multidimensional array and pass it as a parameter in a method and then fill the arrayList with elements and return the new version of the arrayList to be able to use that array in different classes but I get java.lang.NoSuchMethodError: I think the problem is about the way i return the array. I searched but I could not find . How can I do it correctly?

here is my code;

public test{

 public static List<List<String>> 2Darray=new ArrayList<List<String>>(); // TE ERROR IN THIS LINE


 public List<List<String>> fillArray(List<List<String>> array){

BufferedReader in = null;
            ArrayList<String> row = new ArrayList<String>();
            try {
                in = new BufferedReader(new FileReader("sampleFile.txt"));
                String read = null;
                    while ((read = in.readLine()) != null) {
                        String[] splited = read.split("\\s+");                       
                        for(int i=0; i<splited.length ; i++){                           
                            row.add(splited[i]);
                        }                        
                        array.add(row);
                    }                         

                } catch (IOException e) {
                System.out.println("There was a problem: " + e);
                e.printStackTrace();
            } finally {
                try {
                    in.close();
                } catch (IOException e) {
                }
      return array;
}

please include full stack trace and tell us which line is throwing the exception — Sharon Ben Asher
– Sharon Ben Asher, Commented May 10, 2018 at 14:52

OldCurmudgeon · Accepted Answer · 2018-05-10 14:53:12Z

A little tinkering (just getting it to compile) results in this which seems not to have a problem. Perhaps your issue is elsewhere.

public List<List<String>> fillArray(List<List<String>> array) {

    BufferedReader in = null;
    ArrayList<String> row = new ArrayList<String>();
    try {
        in = new BufferedReader(new FileReader("sampleFile.txt"));
        String read = null;
        while ((read = in.readLine()) != null) {
            String[] splited = read.split("\\s+");
            for (int i = 0; i < splited.length; i++) {
                row.add(splited[i]);
            }
            array.add(row);
        }

    } catch (IOException e) {
        System.out.println("There was a problem: " + e);
        e.printStackTrace();
    } finally {
        try {
            in.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    return array;
}

BTW: You should really use try with resources - it is much clearer.

Gabriel Tapizquent · Accepted Answer · 2018-05-10 15:12:21Z

Modified your code a bit so that it compiled, and replaced the reading from a text file to reading a string. There were several issues, but it seems to work. Give it a try.

The main problems I noticed were mismatching curly braces, and starting a variable name with a number.

import java.util.*;
import java.io.*;

public class Main {
  public static List<List<String>> array2D = new ArrayList<List<String>>();

  public List<List<String>> fillArray(List<List<String>> array) {

    BufferedReader in = null;
    ArrayList<String> row = new ArrayList<String>();
    try {
      String str = "Some test text";
      InputStream is = new ByteArrayInputStream(str.getBytes());
      //in = new BufferedReader(new FileReader("sampleFile.txt"));
      in = new BufferedReader(new InputStreamReader(is));
      String read = null;
      while ((read = in.readLine()) != null) {
        String[] splited = read.split("\\s+");                       
        for(int i=0; i<splited.length ; i++) {                           
            row.add(splited[i]);
        }                        
        array.add(row);
      }                         

    } 
    catch (IOException e) {
      System.out.println("There was a problem: " + e);
      e.printStackTrace();
    }
    finally {
      try {
        in.close();
      } 
      catch (IOException e) {
      }
    }
    return array;
  }

  public static void main(String[] args) {
    Main main = new Main();
    List<List<String>> test = main.fillArray(array2D);

    for(int i  = 0; i < test.size(); i++) {
      for(int j = 0; j < test.get(i).size(); j++) {
        System.out.println(test.get(i).get(j));
      }
    }
  }
}

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