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How do you convert a text file into a 2D character array?

I am trying to convert a text file into a 2 dimensional character array. I am part of the way there but the last line of my array is not fully correct. Here's my code:
protected void readMap(String fileName) throws IOException {
BufferedReader br = new BufferedReader(new FileReader(fileName));
char[] chars;
int lines=0;
while (br.readLine() != null) {
lines++;
}
File file = new File(fileName);
try (FileReader reader = new FileReader(file)) {
chars = new char[(int) file.length()];
reader.read(chars);
reader.close();
} catch (IOException e) {
}
int columns = ((int) file.length())/lines;
map = new char[lines][columns];
for(int i=0; i<lines;i++){
for(int j=0;j<columns;j++){
map[i][j] = chars[j%columns+i*columns];
}
}
for(int ro=0; ro<map.length; ro++){
for(int colum=0; colum<(map[0].length); colum++){
System.out.print(map[ro][colum]);
}
}
return null;
}
Here's the output:
##########################
#........................#
#.....###........###.....#
#......G..........G......#
#........................#
#...........E............#
#......G.........G.......#
#........G.....G.........#
#..........###...........#
#........................#
#################
^missing #'s here
I'm very confused on why this is occuring. I've tried changing how I print the array but i'm pretty sure its how its to do with how i've converted the 1d 'chars' array to the 2d 'map' array.
I'm really lost so any help would be much appreciated! Thank you.

I'm guessing your file looks something like this
##########################
#........................#
#.....###........###.....#
#......G..........G......#
#........................#
#...........E............#
#......G.........G.......#
#........G.....G.........#
#..........###...........#
#........................#
##########################
If you print the file length, you will see that the file length is 296
As Your code row = 11 and columns = 26
When you are copying to map you are copying up to 11 * 26 = 286
Try the UPDATED code below
public void readMap(String fileName) throws IOException {
BufferedReader br = new BufferedReader(new FileReader(fileName));
int lines = 0, columns = 0;
String str;
List<String> lineList = new ArrayList<>();
while ((str = br.readLine()) != null && str.length() != 0) {
lines++;
columns = Math.max(columns, str.length()); // as it's not fixed
lineList.add(str);
}
System.out.println("Row : " + lines);
System.out.println("Columns : " + columns);
char[][] map = new char[lines][columns];
for (int i = 0; i < lines; i++) {
String currentLine = lineList.get(i);
int idx = 0;
for (int j = 0; j < currentLine.length(); j++) {
map[i][j] = currentLine.charAt(idx++);
}
}
for (int r = 0; r < map.length; r++) {
for (int c = 0; c < (map[0].length); c++) {
System.out.print(map[r][c]);
}
System.out.println();
}
}

I've just executed the code and the map prints as expected. The issue may be down to the file itself as that is the uncommon factor.
edit:
The results you have observed is because you may have a new line character, or other special character, at the end of or somewhere in the file. Removing this you should see the consistent map you want.
Alternative
protected static void readMap(String fileName) throws IOException {
BufferedReader br = new BufferedReader(new FileReader(fileName));
String line = "";
List<String> lines = new ArrayList<>();
while ((line = br.readLine()) != null) {
lines.add(line);
}
char[][] chars = new char[lines.size()][];
for (int col = 0; col < lines.size(); col++) {
for (int row = 0; row < lines.get(col).length(); row++) {
chars[col] = lines.get(col).toCharArray();
}
}
for (int col = 0; col < chars.length; col++) {
for (int row = 0; row < chars[col].length; row++) {
System.out.print(chars[col][row]);
}
System.out.println();
}
}//My rows and cols may be back to front
Few other notes:
You shouldn't be returning a value from a void method, even null (You'll want to return null if the return type is Void).
Your compiler may complain if you don't initialize chars initially, as mine did. char[] chars = null; would do it in this scenario.

Having trouble with file output

I want to be able to read in 20 random names from the file and put them into a new file. How do i go about this?
public class Assignment2 {
public static void main(String[] args) throws IOException
{
// Read in the file into a list of strings
BufferedReader reader = new BufferedReader(new FileReader("textfile.txt"));
//BufferedWriter bw = new BufferedWriter(new FileWriter("out.txt"));
List<String> lines = new ArrayList<String>();
String line = reader.readLine();
while( line != null ) {
lines.add(line);
line = reader.readLine();
}
// Choose a random one from the list
Random r = new Random();
for (int i = 0; i < 20; i++)
{
int rowNum = r.nextInt(lines.size ());
System.out.println(lines.get(rowNum));
}
}
}

try (BufferedWriter writer = new BufferedWriter(new FileWriter("randomNames.txt"))) {
Random random = new Random();
for (int i = 0; i < 20; i++) {
int rowNum = random.nextInt(lines.size());
writer.write(lines.get(rowNum));
writer.newLine();
}
}
If you need to check if some number was already used, add it to a set:
try (BufferedWriter writer = new BufferedWriter(new FileWriter("randomNames.txt"))) {
Set<Integer> usedNumbers = new HashSet<Integer>(20);
Random random = new Random();
int addedCount = 0;
while (addedCount < 20) {
int rowNum = random.nextInt(lines.size());
if (usedNumbers.add(rowNum)) {
writer.write(lines.get(rowNum));
writer.newLine();
addedCount++;
}
}
}
To check if there is another name with same first character:
private static void containsNameWithSameFirstCharacter(Collection<String> names, String name) {
for (String anotherName : names) {
if (anotherName.charAt(0) == name.charAt(0)) {
return true;
}
}
return false;
}
Then you do:
Random random = new Random();
Set<String> usedNames = new HashSet<String>(20);
while (usedNames.size() < 20) {
int rowNum = random.nextInt(lines.size());
String name = lines.get(rowNum);
if (!containsNameWithSameFirstCharacter(usedNames, name)) {
usedNames.add(name);
writer.write(name);
writer.newLine();
}
}

replace random number of characters at random position with wildcard

I am trying to create a program which would replace random number of characters at random position with "*". Star is letter used in main program and it is replaced with "." a wildcard to matches any possible result.
So far I manage to create the code you see bellow. It replaces exactly 1 character of specific word.
Any help from here on now would be much appreciated.
EXAMPLE:
Input word: MOUSE
RANDOM GENERATOR for how much characters to replace: 3
RANDOM GENERATOR at which places to replace: 1, 3, 5
RESULT: *O*S*
public class random_2 {
public static void main(String[] args) {
String test;
int dolzina = 0;
String outputFile = "random_2.txt";
ArrayList<String> list = new ArrayList();
try {
File file = new File("random1.txt");
FileReader fileReader = new FileReader(file);
BufferedReader bufferedReader = new BufferedReader(fileReader);
String vrstica;
while ((vrstica = bufferedReader.readLine()) != null) {
list.add(vrstica);
// dolzina=list.size();
// System.out.println(dolzina);
}
FileWriter fileWriter = new FileWriter(outputFile);
PrintWriter out = new PrintWriter(fileWriter);
for (int idx = 0; idx <= list.size(); ++idx) {
test=list.get(idx);
dolzina=test.length();
Random rGenerator = new Random();
for (int i = 0; i<= dolzina; ++i) {
int randomInt = rGenerator.nextInt(dolzina);
StringBuilder beseda = new StringBuilder(test);
beseda.setCharAt(randomInt, '*');
System.out.println(beseda);
dolzina=0;
}}
System.out.println("Done.");
} catch (IOException e) {
e.printStackTrace();
}
}
}

Modified your code and its working:
try {
File file = new File("random1.txt");
FileReader fileReader = new FileReader(file);
BufferedReader bufferedReader = new BufferedReader(fileReader);
String vrstica = bufferedReader.readLine();
while (vrstica != null) {
list.add(vrstica);
vrstica = bufferedReader.readLine();
// dolzina=list.size();
// System.out.println(dolzina);
}
FileWriter fileWriter = new FileWriter(outputFile);
PrintWriter out = new PrintWriter(fileWriter);
for (int idx = 0; idx < list.size(); ++idx) {
test = list.get(idx);
dolzina = test.length();
Random rGenerator = new Random();
StringBuilder beseda = new StringBuilder(test);
for (int i = 0; i < dolzina; ++i) {
int randomInt = rGenerator.nextInt(dolzina);
beseda.setCharAt(randomInt, '*');
System.out.println(beseda);
}
out.print(beseda);
out.close();
}

you can try something like this:
String mask(String s, int charsToMask){
if(s.length() < charsToMask) throw new IllegalArgumentException();
List<Integer> shuffle = new ArrayList<>(s.length())
for (int i = 0; i < s.length(); i++) {
shuffle.add(i, i);
}
Collections.shuffle(shuffle);
StringBuilder sb = new StringBuilder(s)
for (int i = 0; i < charsToMask; i++) {
sb.setCharAt(shuffle.get(i).intValue(), (char)'*')
}
return sb.toString()
}
print mask("MOUSE", 3)

Reading CSV file without third-party libraries

I'm trying to read a csv file into either an ArrayList or a String [][] array. In this I'm trying to read it into a list and then form the list, using a tokenizer, into an array. The csv file have 7 columns (A - G) and 961 rows (1-961). My for loop for the 2D array keeps returning a null pointer, but I think it should be working..
public class FoodFacts
{
private static BufferedReader textIn;
private static BufferedReader foodFacts;
static int numberOfLines = 0;
static String [][] foodArray;
public static String aFact;
static int NUM_COL = 7;
static int NUM_ROW = 961;
// Make a random number to pull a line
static Random r = new Random();
public static void main(String[] args)
{
try
{
textIn = new BufferedReader(new InputStreamReader(System.in));
foodFacts= new BufferedReader(new FileReader("foodfacts.csv"));
Scanner factFile = new Scanner(foodFacts);
List<String> facts = new ArrayList<String>();
String fact;
System.out.println("Please type in the food you wish to know about.");
String request = textIn.readLine();
while ( factFile.hasNextLine()){
fact = factFile.nextLine();
StringTokenizer st2 = new StringTokenizer(fact, ",");
//facts.add(fact);
numberOfLines++;
while (st2.hasMoreElements()){
for ( int j = 0; j < NUM_COL ; j++) {
for (int i = 0; i < NUM_ROW ; i++){
foodArray [j][i]= st2.nextToken(); //NULL POINTER HERE
System.out.println(foodArray[j][i]);
}
}
}
}
}
catch (IOException e)
{
System.out.println ("Error, problem reading text file!");
e.printStackTrace();
}
}
}

Initialize your foodArray as foodArray = new String[NUM_ROW][NUM_COL]; before using it.
Also, there is no need for inner for loop as you are reading one row at a time.
use numberOfLines as row:
while ( factFile.hasNextLine() && numberOfLines < NUM_ROW){
fact = input.nextLine();
StringTokenizer st2 = new StringTokenizer(fact, ",") ;
//facts.add(fact);
while (st2.hasMoreElements()){
for ( int j = 0; j < NUM_COL ; j++) {
foodArray [numberOfLines][j]= st2.nextToken();
System.out.println(foodArray[numberOfLines][i]);
}
}
numberOfLines++;
}
Alternatively, I think you can use split to get all columns as once e.g.
while ( factFile.hasNextLine() && numberOfLines < NUM_ROW){
fact = input.nextLine();
foodArray [numberOfLines++] = fact.split(",");
}
One question: Is there any specific purpose for declaring all variables as static class variables? Most of them fit as local variable inside the method e.g. numberOfLines?

You can use this String [][] foodArray = csvreadString(filename); method. It actually reads the file twice, but I don't know how to get the csv dimension without reading the data (you need the dimension in order to initialize the array), and this is very fast in comparison to other methods that I tried.
static public class PairInt {
int rows = 0;
int columns = 0;
}
static PairInt getCsvSize(String filename) throws Throwable {
PairInt csvSize = new PairInt();
BufferedReader reader = new BufferedReader(new FileReader(new File(filename)));
String line;
while ((line = reader.readLine()) != null) {
if (csvSize.columns == 0) {
csvSize.columns = line.split(",").length;
}
csvSize.rows++;
}
reader.close();
return csvSize;
}
static String[][] csvreadString(String filename) throws Throwable {
PairInt csvSize = getCsvSize(filename);
String[][] data = new String[csvSize.rows][csvSize.columns];
BufferedReader reader = new BufferedReader(new FileReader(new File(filename)));
for (int i = 0; i < csvSize.rows; i++) {
data[i] = reader.readLine().split(",");
}
return data;
}

Read .txt file and store in 2-D char array java

I am kind of stuck. How do I get this to work or are there a better way? Please give code examples.
public char[][] charmap = new char[SomeInts.amount][SomeInts.amount];
public void loadMap() throws IOException{
BufferedReader in = new BufferedReader(new FileReader("map1.txt"));
String line = in.readLine();
while (line != null){
int y = 0;
for (int x = 0; x < line.length(); x++){
//Error
charmap[x][y] = line[x];
//
}
y++;
}
}

The syntax line[x] is reserved for arrays. A String is not an array. You could use the String#charAt method and write:
charmap[x][y] = line.charAt(x);

Use String.charAt(int) to fetch character from strings..

Try this.
char[][] mapdata = new char[SomeInts.amount][SomeInts.amount];
public void loadMap() throws IOException{
BufferedReader in = new BufferedReader(new FileReader("map1.txt"));
String line = in.readLine();
ArrayList<String> lines = new ArrayList<String>();
// Load all the lines
while (line != null){
lines.add(line);
}
// Parse the data
for (int i = 0; i < lines.size(); i++) {
for (int j = 0; j < lines.get(i).length(); j++) {
mapdata[j][i] = lines.get(i).charAt(j);
}
}
}
Hope this helps.