public static void writeMatrixToFile(Matrix m, String filename) {

        try (FileWriter writer = new FileWriter(filename, false)) {
            String strForWrite = "";

            for (int i = 1; i < m.getRowCount(); i++) {
                for (int j = 1; j < m.getColCount(); j++) {
                    strForWrite += m.get(i, j) + " ";
                }
                strForWrite += "\n";
            }

            writer.write(strForWrite);
            writer.flush();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (MatrixIndexException e) {
            e.printStackTrace();
        }
    }

    public static Matrix loadMatrixFromFile(Matrix m, String filename) {

        try (FileWriter writer = new FileWriter(filename, false)) {
            String strForWrite = "";

            writer.write(String.valueOf(m.getRowCount()));
            writer.write("\n");
            writer.write(String.valueOf(m.getColCount()));
            writer.write("\n");

            for (int i = 1; i < m.getRowCount(); i++) {
                for (int j = 1; j < m.getColCount(); j++) {
                    strForWrite += m.get(i, j) + " ";
                }
                strForWrite += "\n";
            }

            writer.write(strForWrite);
            writer.flush();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (MatrixIndexException e) {
            e.printStackTrace();
        } catch (Exception e) {
        }
    }

package matrix;

import java.util.LinkedList;
import java.util.List;

public class Main extends Exception {

    public static void main(String[] args) throws MatrixIndexException {

        Matrix2D mA = new Matrix2D(100, 100);
        
        MatrixUtils.fillByRandom(mA);
        
        MatrixUtils.writeMatrixToFile(mA, "C://Data//1.txt");
        
        System.out.println(mA.toString());

 public static void writeMatrixToFile(Matrix m, String filename) {


        try(FileWriter writer = new FileWriter(filename, false)){
            String strForWrite = "";
            
            writer.write(String.valueOf(m.getRowCount()));
            writer.write("\n");
            writer.write(String.valueOf(m.getColCount()));
            writer.write("\n");

            for (int i = 1; i < m.getRowCount(); i++){
                for (int j = 1; j < m.getColCount(); j++){
                    
                    strForWrite += m.get(i,j) + " ";
                }
                strForWrite += "\n";
            }

            writer.write(strForWrite);
            writer.flush();
        }catch (IOException e){
            e.printStackTrace();
        }catch(MatrixIndexException e){
             e.printStackTrace();
        }
    }

    public Matrix loadMatrixFromFile(String filename){
        try(FileReader reader = new FileReader(filename)){
            String strFromFile = "";

            while (reader.ready()){
                strFromFile += (char)reader.read();
            }

            String[] arr = strFromFile.split(" |\n");
            Matrix result = new Matrix(Integer.valueOf(arr[0]),Integer.valueOf(arr[1]));

            int row = 0;
            int col = 0;

            for (int i = 2; i < arr.length; i++){
                if (!arr[i].equals("")){
                    result.put(row, col) = Integer.valueOf(arr[i]);
                    col++;
                    if (col == result.getColCount()){
                        col = 0;
                        row++;
                    }
                }
            }

            return result;
        }catch (Exception e){
            e.printStackTrace();
        }
        return null;
    }
}

100
100
1 24 44 22 36 24 2 23 12 26 16 22 7 3 10 47 47 20 7 47 7 30 18 23 7 28 30 31 14 13 32 32 22 46 3 7 31 6 1 1 15 12 48 10 30 7 24 13 40 18 41 22 47 2 36 20 28 27 34 8 49 2 19 28 27 46 4 15 27 22 3 1 32 0 9 32 8 42 43 42 3 39 23 15 48 33 27 45 14 31 1 44 40 6 4 15 27 49 44 
1 21 18 23 18 40 26 25 14 27 33 14 5 24 11 24 13 45 22 8 12 16 46 0 17 15 9 48 6 46 8 23 28 29 34 20 44 32 28 4 38 18 23 2 37 34 29 3 48 20 24 41 33 7 0 16 48 4 3 36 25 46 36 3 32 46 17 49 10 29 11 25 29 41 21 48 24 46 4 37 8 48 29 36 16 38 3 44 33 48 5 19 49 15 28 12 25 25 32 
27 20 19 22 34 3 5 8 2 5 30 21 25 19 47 15 31 0 14 31 22 37 12 4 17 29 23 2 6 26 27 9 40 1 39 22 42 42 22 20 6 2 35 4 40 44 27 26 47 36 10 36 8 9 44 14 16 5 19 9 33 28 5 32 35 0 9 27 29 49 44 2 27 4 33 20 4 39 44 49 13 22 1 26 16 19 47 5 20 45 18 48 12 46 46 21 35 12 43 
38 34 19 32 42 34 31 46 39 6 7 38 32 42 8 12 6 5 21 39 18 9 38 6 7 48 26 37 17 30 47 21 41 47 29 44 40 29 20 0 31 48 3 7 37 49 2 27 13 45 2 36 9 15 33 20 22 8 28 29 40 31 22 1 18 27 11 6 0 40 11 45 20 27 21 31 12 22 14 34 15 9 15 24 44 44 29 7 1 32 6 13 31 21 17 2 19 25 49 
46 7 16 11 4 5 18 43 16 9 22 10 41 7 45 11 18 36 28 31 43 15 36 42 33 28 41 17 45 9 17 4 1 29 16 41 40 18 8 23 34 17 21 48 43 25 15 29 35 49 20 11 0 7 18 33 49 49 44 35 12 19 14 42 34 1 38 42 18 6 49 34 17 33 2 2 4 15 35 21 0 37 3 19 26 26 34 32 35 45 7 19 33 20 18 28 43 17 4 
24 9 44 40 22 1 21 7 39 16 15 20 37 9 43 36 17 26 33 26 48 7 43 6 38 18 33 28 34 21 33 43 28 9 3 8 37 25 25 9 8 35 43 12 2 48 18 23 45 15 26 3 5 3 10 37 3 39 32 22 40 18 48 43 9 14 5 40 35 18 22 49 7 3 20 48 49 19 38 19 39 7 25 3 24 47 37 39 25 48 21 29 35 9 4 38 15 32 30 
27 47 11 15 31 39 37 26 8 28 33 46 19 1 26 22 34 0 17 11 3 42 36 39 32 13 25 9 44 15 40 35 26 8 46 48 38 10 21 41 0 25 7 31 3 45 37 46 35 6 46 6 7 39 4 41 26 24 25 21 22 13 24 4 37 2 9 18 30 18 46 49 33 11 31 13 31 43 8 5 44 46 39 9 30 21 5 18 39 4 28 21 47 1 5 0 17 3 30 
11 48 16 25 26 31 49 37 19 28 4 47 19 19 13 19 41 45 39 12 40 4 37 2 40 45 46 23 17 49 10 6 25 4 3 29 46 22 41 0 19 25 17 24 20 21 5 25 42 49 28 32 11 27 26 22 42 18 18 7 33 2 36 5 2 36 11 27 15 2 36 33 12 22 41 20 10 23 33 33 30 23 3 29 16 21 47 18 31 38 42 30 44 16 5 24 25 11 37 
36 25 41 27 10 33 29 19 39 5 45 32 47 30 9 43 48 13 13 32 40 49 13 20 7 31 39 40 2 43 26 21 17 48 9 49 33 14 3 25 4 44 49 38 6 37 37 38 20 17 43 3 32 44 3 29 44 27 47 16 1 33 2 15 2 30 42 8 4 30 2 26 13 3 38 46 31 2 49 8 12 37 28 31 41 27 16 4 32 38 4 9 8 1 13 15 7 5 49 
20 24 40 2 22 30 46 8 38 13 8 13 31 45 12 37 2 45 5 21 38 48 8 26 39 7 31 19 10 17 29 13 25 36 1 27 5 43 37 5 34 47 49 28 46 5 42 41 7 38 37 33 47 36 3 47 13 18 36 15 30 39 40 7 28 14 29 20 19 1 42 14 39 14 26 42 36 19 43 31 5 44 32 18 48 46 30 11 14 29 45 39 45 4 21 2 21 39 22 
42 37 26 18 45 23 43 17 2 20 49 46 23 22 3 35 12 19 11 2 20 10 18 41 26 10 3 40 24 39 13 25 17 25 38 30 40 11 38 28 47 35 11 3 28 33 5 46 16 0 4 15 45 9 29 20 2 10 28 10 48 6 5 37 5 44 17 3 12 5 33 28 25 1 22 47 4 39 41 30 14 37 11 12 7 45 47 14 6 47 11 0 37 18 0 29 39 32 49 
33 4 17 47 13 42 9 37 40 12 31 30 25 32 44 10 36 4 28 18 

Exception in thread "main" java.lang.RuntimeException: Uncompilable source code - Erroneous sym type: java.lang.StringBuilder.Append
	at matrix.MatrixUtils.writeMatrixToFile(MatrixUtils.java:119)
	at matrix.Main.main(Main.java:19)
C:\Users\Adil\AppData\Local\NetBeans\Cache\8.2\executor-snippets\run.xml:53: Java returned: 1
СБОРКА ЗАВЕРШЕНА СО СБОЕМ (общее время: 0 секунд)