Develop Reference

Split lines with "," and do a trim on every element [duplicate]

This is some code that I found to help with reading in a 2D Array, but the problem I am having is this will only work when reading a list of number structured like:
73
56
30
75
80
ect..
What I want is to be able to read multiple lines that are structured like this:
1,0,1,1,0,1,0,1,0,1
1,0,0,1,0,0,0,1,0,1
1,1,0,1,0,1,0,1,1,1
I just want to essentially import each line as an array, while structuring them like an array in the text file.
Everything I have read says to use scan.usedelimiter(","); but everywhere I try to use it the program throws straight to the catch that replies "Error converting number". If anyone can help I would greatly appreciate it. I also saw some information about using split for the buffered reader, but I don't know which would be better to use/why/how.
String filename = "res/test.txt"; // Finds the file you want to test.
try{
FileReader ConnectionToFile = new FileReader(filename);
BufferedReader read = new BufferedReader(ConnectionToFile);
Scanner scan = new Scanner(read);
int[][] Spaces = new int[10][10];
int counter = 0;
try{
while(scan.hasNext() && counter < 10)
{
for(int i = 0; i < 10; i++)
{
counter = counter + 1;
for(int m = 0; m < 10; m++)
{
Spaces[i][m] = scan.nextInt();
}
}
}
for(int i = 0; i < 10; i++)
{
//Prints out Arrays to the Console, (not needed in final)
System.out.println("Array" + (i + 1) + " is: " + Spaces[i][0] + ", " + Spaces[i][1] + ", " + Spaces[i][2] + ", " + Spaces[i][3] + ", " + Spaces[i][4] + ", " + Spaces[i][5] + ", " + Spaces[i][6]+ ", " + Spaces[i][7]+ ", " + Spaces[i][8]+ ", " + Spaces[i][9]);
}
}
catch(InputMismatchException e)
{
System.out.println("Error converting number");
}
scan.close();
read.close();
}
catch (IOException e)
{
System.out.println("IO-Error open/close of file" + filename);
}
}

I provide my code here.
public static int[][] readArray(String path) throws IOException {
//1,0,1,1,0,1,0,1,0,1
int[][] result = new int[3][10];
BufferedReader reader = new BufferedReader(new FileReader(path));
String line = null;
Scanner scanner = null;
line = reader.readLine();
if(line == null) {
return result;
}
String pattern = createPattern(line);
int lineNumber = 0;
MatchResult temp = null;
while(line != null) {
scanner = new Scanner(line);
scanner.findInLine(pattern);
temp = scanner.match();
int count = temp.groupCount();
for(int i=1;i<=count;i++) {
result[lineNumber][i-1] = Integer.parseInt(temp.group(i));
}
lineNumber++;
scanner.close();
line = reader.readLine();
}
return result;
}
public static String createPattern(String line) {
char[] chars = line.toCharArray();
StringBuilder pattern = new StringBuilder();;
for(char c : chars) {
if(',' == c) {
pattern.append(',');
} else {
pattern.append("(\\d+)");
}
}
return pattern.toString();
}

The following piece of code snippet might be helpful. The basic idea is to read each line and parse out CSV. Please be advised that CSV parsing is generally hard and mostly requires specialized library (such as CSVReader). However, the issue in hand is relatively straightforward.
try {
String line = "";
int rowNumber = 0;
while(scan.hasNextLine()) {
line = scan.nextLine();
String[] elements = line.split(',');
int elementCount = 0;
for(String element : elements) {
int elementValue = Integer.parseInt(element);
spaces[rowNumber][elementCount] = elementValue;
elementCount++;
}
rowNumber++;
}
} // you know what goes afterwards

Since it is a file which is read line by line, read each line using a delimiter ",".
So Here you just create a new scanner object passing each line using delimter ","
Code looks like this, in first for loop
for(int i = 0; i < 10; i++)
{
Scanner newScan=new Scanner(scan.nextLine()).useDelimiter(",");
counter = counter + 1;
for(int m = 0; m < 10; m++)
{
Spaces[i][m] = newScan.nextInt();
}
}

Use the useDelimiter method in Scanner to set the delimiter to "," instead of the default space character.
As per the sample input given, if the next row in a 2D array begins in a new line, instead of using a ",", multiple delimiters have to be specified.
Example:
scan.useDelimiter(",|\\r\\n");
This sets the delimiter to both "," and carriage return + new line characters.

Why use a scanner for a file? You already have a BufferedReader:
FileReader fileReader = new FileReader(filename);
BufferedReader reader = new BufferedReader(fileReader);
Now you can read the file line by line. The tricky bit is you want an array of int
int[][] spaces = new int[10][10];
String line = null;
int row = 0;
while ((line = reader.readLine()) != null)
{
String[] array = line.split(",");
for (int i = 0; i < array.length; i++)
{
spaces[row][i] = Integer.parseInt(array[i]);
}
row++;
}
The other approach is using a Scanner for the individual lines:
while ((line = reader.readLine()) != null)
{
Scanner s = new Scanner(line).useDelimiter(',');
int col = 0;
while (s.hasNextInt())
{
spaces[row][col] = s.nextInt();
col++;
}
row++;
}
The other thing worth noting is that you're using an int[10][10]; this requires you to know the length of the file in advance. A List<int[]> would remove this requirement.

Filling a double[][] from the CSV file

I have this CSV file:
World Development Indicators
Number of countries,4
Country Name,2005,2006,2007,2008,2009,2010,2011,2012,2013,2014
Bangladesh,6.28776238,13.20573922,23.46762823,30.16828408,34.35334451,44.94535882,55.19256723,62.82023906,74.42964608,80.03535051
"Bahamas, The",69.21279415,75.37855087,109.340767,102.7875065,101.2186453,118.8292307,81.5628489,80.65383375,76.05187427,82.29635806
Brazil,46.31418452,53.11025849,63.67475185,78.5549801,87.54187651,100.8810115,119.0023853,125.0018521,135.3050481,138.9514906
Germany,94.55486999,102.2828888,115.1403608,126.5575074,126.2280577,106.4836959,109.6595675,111.5940398,120.9211651,120.4201855
I am trying to store countries' data(double once) into a matrix(double[][]). Here is the code that I have so far:
public double[][] getParsedTable() throws IOException {
double[][] table = new double[4][10];
String row;
int indexRow = 0;
int indexColumn = 0;
BufferedReader br = new BufferedReader(new FileReader(fileName));
br.readLine();
br.readLine();
String line = br.readLine();
while(line != null && !line.isEmpty()){
line = br.readLine();
String[] array = line.split(",(?=(?:[^\"]*\"[^\"]*\")*[^\"]*$)", -1);
for(int i = 1; i < array.length; i++){
table[indexRow][indexColumn] = Double.parseDouble(array[i]);
indexColumn++;
}
indexColumn = 0;
indexRow++;
}
System.out.print(Arrays.deepToString(table));
return table;
}
I am getting an arror : NullPointerException at:
String[] array = line.split(",(?=(?:[^\"]*\"[^\"]*\")*[^\"]*$)", -1);
I cant figure out why. I tried different combinations. nothing seems to work. It seems to pick up the numbers from the CSV file and store them, but when I call:
System.out.print(Arrays.deepToString(table));
it does not print out anything, hence I cant check if its stored properly or not. Could you tell me: 1. Why I am getting an error. 2. Why System.out.println does not print out an array. Thanks

If we assume that name of a country will not contain a digit and country name and numbers will be only comma separated, then following can be done without regex. I have changed file reading a little bit because it can run into issues.
public double[][] getParsedTable() throws IOException {
double[][] table = new double[4][10];
int indexRow = 0;
int indexColumn = 0;
BufferedReader br = new BufferedReader(new FileReader(fileName));
br.readLine(); // ignore first line
br.readLine(); // ignore second line
br.readLine(); // ignore third line (contains title)
String line;
while (true) {
line = br.readLine();
if (line == null) break; // end of file reading
int index = 0;
while (true) {
index = line.indexOf(",", index) + 1;
if (Character.isDigit(line.charAt(index))) {
break;
}
}
// from index, line is expected to contain comma separated numbers
String[] array = line.substring(index).split(",");
for (int i = 0; i < array.length; i++) {
table[indexRow][indexColumn] = Double.parseDouble(array[i]);
indexColumn++;
}
indexColumn = 0;
indexRow++;
}
System.out.print(Arrays.deepToString(table));
return table;
}

In the csv, first 3 lines are not real country's data. So read in line-4 before while loop starts.
In while loop, first finish the processing of line string first. Eg: regular expression check & assign split data into table.
Then only read in next line at end of while loop, to be processed in next iteration.
Feel free to try this out:
public double[][] getParsedTable() throws IOException {
double[][] table = new double[4][10];
int indexRow = 0;
int indexColumn = 0;
// check whether you need to handle any exception for this
BufferedReader br = new BufferedReader(new FileReader(fileName));
String line = null;
try {
// line 1-3 are not real country's data
br.readLine();
br.readLine();
br.readLine();
// first country data begin at line 4
line = br.readLine();
} catch (IOException e) {
e.printStackTrace();
}
while (line != null && !line.isEmpty()) {
String[] array = line.split(",(?=(?:[^\"]*\"[^\"]*\")*[^\"]*$)", -1);
for (int i = 1; i < array.length; i++) {
table[indexRow][indexColumn] = Double.parseDouble(array[i]);
indexColumn++;
}
indexColumn = 0;
indexRow++;
// read next line only at end of loop, not beginning of loop
// line is ready to be processed at next iteration
try {
line = br.readLine();
} catch (IOException e) {
e.printStackTrace();
}
}
System.out.print(Arrays.deepToString(table));
return table;
}

Arrays.deepToString is wrong. You are passing in an array of primitives. When you pass it in, you pass in double[][]. This is interpeted as Object[] where the objects are double[], so it will try to print double[] objects, and not print doubles.
One solution is to create an array Double[][].
Change
double[][] table = new double[4][10];
to
Double[][] table = new Double[4][10];
Autoboxing will convert each double to a Double. Since Double is an object and not a primitive, deepToString will print out each Double individually. If you read the javadoc for deepToString it explains that it operates recursively on arrays of reference type, not on primitive arrays.
If you want to stick with double[][]
for (int i = 0; i < table.length; i++) {
for (int j = 0; j < table[i].length; j++) {
System.out.print(table[i][j]);
System.out.print(' ');
}
System.out.println();
}

Reading a text file into a 2D array

I need to read a text file into a 2D array, I can read files into the program perfectly fine (see my code below) however I cannot get my head around how to read them into a 2D array. The array the function is reading into is a global array hence why it's not in the function.
Also I won't know the amount of rows the array has at first (currently set at 300 as it won't be over this) and I know this could cause a problem, I've seen some people suggest using ArrayLists however I have to have a 2D array so I was also wondering if there was a way to change an ArrayList to a 2D array and if this would be more effective?
public static String readMaze(String fileName) {
String line = null;
try {
FileReader fileReader = new FileReader(fileName);
BufferedReader bufferedReader = new BufferedReader(fileReader);
while ((line = bufferedReader.readLine()) != null) {
System.out.println(line);
for (int i = 0; i < mazeNew.length; i++) {
for (int j = 0; j < mazeNew[i].length; j++) {
// mazeNew[i][j] = ; - this is where I think something needs to be added
}
}
}
bufferedReader.close();
}
catch (FileNotFoundException ex) {
System.out.println("Unable to open file: " + fileName);
}
catch (IOException ex) {
System.out.println("Error reading file: " + fileName);
}
return fileName;
}
example text file:
11 4
5 6
4 6
0 5
3 5
8 7
1 4

There's a few options here, but generally you'll want to use the Java Scanner class as it's designed for exactly this kind of thing. Alternatively, use an existing structured data format (like JSON or XML) and an existing parser to go with it - the advantage being you can make use of a vast amount of tools and libraries which deal with those formats and don't have to re-invent anything.
However, following through with the scanner approach, it would be like so:
public static ArrayList<int[]> readMaze(String fileName) {
// Number of ints per line:
int width=2;
// This will be the output - a list of rows, each with 'width' entries:
ArrayList<int[]> results=new ArrayList<int[]>();
String line = null;
try {
FileReader fileReader = new FileReader(fileName);
BufferedReader bufferedReader = new BufferedReader(fileReader);
Scanner mazeRunner = new Scanner(bufferedReader);
// While we've got another line..
while (mazeRunner.hasNextLine()) {
// Setup current row:
int[] row = new int[width];
// For each number..
for (int i = 0; i < width; i++) {
// Read the number and add it to the current row:
row[i] = mazeRunner.nextInt();
}
// Add the row to the results:
results.add(row);
// Go to the next line (optional, but helps deal with erroneous input files):
if ( mazeRunner.hasNextLine() ) {
// Go to the next line:
mazeRunner.nextLine();
}
}
mazeRunner.close();
}
catch (FileNotFoundException ex) {
System.out.println("Unable to open file: " + fileName);
}
catch (IOException ex) {
System.out.println("Error reading file: " + fileName);
}
return results;
}

If you have fixed no. of columns you can use this, but make sure input file must follow the same no of coulmns.
FileReader fileReader = new FileReader(fileName);
Scanner sc = new Scanner(fileReader);
int row=0, col=0;
while ((sc.hasNext()) != null) {
if(col < colSize){ //colSize is size of column
mazeNew[row][col]= sc.nextInt();
}
else{
col=0;
row++;
}
}

Below is the core logic, you would probably also like to to handle some errors, such as how many elements is a line split into, are there empty lines, etc.
List<String[]> list = new ArrayList<>();
Pattern pattern = Pattern.compile("\\s+");
while ((line = bufferedReader.readLine()) != null) {
list.add(pattern.split(line, -1));
}
String[][] mazeNew = list.toArray(new String[0][0]);

Something like this would work
it wont only read 2d text files .. it should work fine with any dimensions
public class Utile{
public static ArrayList<int[]> readMaze(String path){
ArrayList<int[]> result = new ArrayList<>();
try{
Scanner sc = new Scanner(new File(path));
String[] temp;
String line;
while(sc.hasNextLine()){
line = sc.nextLine();
if (line.length() != 0){ //if the line is empty it will cause NumberFormatException
temp = line.split(" ");
int[] val = new int[temp.length];
for(int i = 0;i < temp.length;i++){
val[i] = Integer.pareseInt(temp[i]);
}
result.add(val);
}
}
sc.close();
}catch(Exception e){
e.printStackTrace(); //just log it for now
}
return result;
}
}

I am not a java expert, but in PHP I would do it with explode(). But I found an example how to do the same in java using string.split(). The result is the same ... an 2D Array of the content. If possible you should try to add an delimiter to the rows inside that text document. But you could split the rows on the space character either.
Example:
String foo = "This,that,other";
String[] split = foo.split(",");
StringBuilder sb = new StringBuilder();
for (int i = 0; i < split.length; i++) {
sb.append(split[i]);
if (i != split.length - 1) {
sb.append(" ");
}
}
String joined = sb.toString();

Txt file into a double 2d array

I am trying to read a txt file into a array of doubles. I am using the following code which reads every line of the file:
String fileName="myFile.txt";
try{
//Create object of FileReader
FileReader inputFile = new FileReader(fileName);
//Instantiate the BufferedReader Class
BufferedReader bufferReader = new BufferedReader(inputFile);
//Variable to hold the one line data
String line;
// Read file line by line and print on the console
while ((line = bufferReader.readLine()) != null) {
System.out.println(line);
}
//Close the buffer reader
bufferReader.close();
}catch(Exception e){
System.out.println("Error while reading file line by line:"
+ e.getMessage());
}
However I want to store the txt file into a 2d double array.
I ve tried the above to load also the dimension of the txt. But I am having problems with the exceptions catch (NoSuchElementException e), it seems that it couldnt read the file.
try {
while (input.hasNext()) {
count++;
if (count == 1) {
row = input.nextInt();
r = row;
System.out.println(row);
continue;
} else if (count == 2) {
col = input.nextInt();
System.out.println(col);
c = col;
continue;
} else {
output_matrix = new double[row][col];
for (int i = 0; i < row; i++) {
for (int j = 0; j < col; j++) {
String el = input.next();
Double temp = Double.valueOf(el);
double number = temp.doubleValue();
//output_matrix[i][j] = el;
output_matrix[i][j] = number;
//System.out.print(output_matrix[i][j]+" ");
}
//System.out.println();
}
}
}
} catch (NoSuchElementException e) {
System.err.println("Sfalma kata ti tropopoisisi toy arxeioy");
System.err.println(e.getMessage()); //emfanisi tou minimatos sfalmatos
input.close();
System.exit(0);
} catch (IllegalStateException e) {
System.err.println("Sfalma kata ti anagnosi toy arxeioy");
System.exit(0);
}

You might want to be using the Scanner class for it, especially the Scanner.nextDouble() method.
Also, if you don't know in advance the dimensions of the array - I'd suggest using an ArrayList instead of a regular array.
Code example:
ArrayList<ArrayList<Double>> list = new ArrayList<>();
while ((line = bufferReader.readLine()) != null) {
ArrayList<Double> curr = new ArrayList<>();
Scanner sc = new Scanner(line);
while (sc.hasNextDouble()) {
curr.add(sc.nextDouble());
}
list.add(curr);
}

At firs declare a list and collect into it all read lines:
List<String> tempHistory = new ArrayList<>();
while ((line = bufferReader.readLine()) != null) {
tempHistory.add(line);
}
Then, after bufferReader.close(); convert this tempHistory list into double[][] array.
double[][] array = new double[tempHistory.size()][];
for (int i = 0; i < tempHistory.size(); i++) {
final String currentString = tempHistory.get(i);
final String[] split = currentString.split(" ");
array[i] = new double[split.length];
for (int j = 0; j < split.length; j++) {
array[i][j] = Double.parseDouble(split[j]);
}
}
It works, but as I added in comments, this is a not so good solution, and is better to use Collections instead of array.
BTW, it works even the rows lengths are different for different lines.

Java Reading a 2D array from a file

Say I have a file of the following format:
3
4
1,2,3,4
5,6,7,8
9,10,11,12
The first two lines of the file represent the number of rows and columns of a 2D array. Thereafter, each line represents the values of each row of the 2D array. I am trying to read this file and create a 2D integer array in java. I tried the following code:
public class PrintSpiral {
private static BufferedReader in = null;
private static int rows = 0;
private static int columns = 0;
private static int [][] matrix = null;
public static void main(String []args) throws Exception {
try {
String filepath = args[0];
int lineNum = 0;
int row=0;
in = new BufferedReader(new FileReader(filepath));
String line = in.readLine();
while(line!=null) {
lineNum++;
if(lineNum==1) {
rows = Integer.parseInt(line);
System.out.println("The number of rows of the matrix are: " + rows);
} else if(lineNum==2) {
columns = Integer.parseInt(line);
System.out.println("The number of columns of the matrix are: " + columns);
matrix = new int[rows][columns];
} else {
String [] tokens = line.split(",");
for (int j=0; j<tokens.length; j++) {
System.out.println("I am filling the row: " + row);
matrix[row][j] = Integer.parseInt(tokens[j]);
}
row++;
}
}
} catch (Exception ex) {
System.out.println("The code throws an exception");
System.out.println(ex.getMessage());
} finally {
if (in!=null) in.close();
}
System.out.println("I am printing the matrix: ");
for (int i=0; i < rows; i++) {
for(int j=0; j < columns; j++)
System.out.print(matrix[i][j]);
System.out.println("");
}
}
}
The output that I see is:
The number of rows of the matrix are: 3
The number of columns of the matrix are: 3
I am filling the row: 0
I am filling the row: 1
I am filling the row: 2
I am filling the row: 3
The code throws an exception
3
I am printing the matrix:
300
300
300
3 0 0 0 0 0 3 3 0
Clearly, the java code is not reading the file correctly. Also, my code throws an exception. I am not sure what causes this exception. I can't seem to figure out what's wrong with my code. Thanks!

change
in = new BufferedReader(new FileReader(filepath));
String line = in.readLine();
while(line!=null) { .....
to
in = new BufferedReader(new FileReader(filepath));
String line = null;
while((line = in.readLine()) !=null) { .....
to read a new line at the start of each loop

You (very obviously) don't have a readLine() inside your loop, so it only ever reads the first line of the file.
Why bother having to specify the rows/columns? Why not just figure it out from the data itself?

at the end of the while loop, add in.readline();
you are just keeping the same line forever and looping on it.