Develop Reference

How to put each word in a sentence inside a 2d array from a csv file

I'm trying to read a text file and put each comma separated value in an array and put all of them inside a 2d array.But the code I have right now puts the whole line in the array
Scanner sc = new Scanner(new BufferedReader(new FileReader(path)));
int rows = 3;
int columns = 1;
String[][] myArray = new String[rows][columns];
while (sc.hasNextLine()) {
for (int i = 0; i < myArray.length; i++) {
String[] line = sc.nextLine().trim().split(" " + ",");
for (int j = 0; j < line.length; j++) {
myArray[i][j] = line[j];
}
}
}
System.out.println(Arrays.deepToString(myArray));
This is the text file:
A6,A7
F2,F3
F6,G6
Output
[[A6,A7], [F2,F3], [F6,G6]]
Expected Output
[[A6],[A7],[F2],[F3],[F6],[G6]]

The problem is that you are assigning the entire 2D array instead of just each item.
Here are several alternatives.
Use Files.lines to stream the file.
splitting on a comma creates the 1D array of two elements for each line
flatMap that to stream each item.
that map that to an array of one item.
then just store them in a 2D array.
String[][] array = null;
try {
array = Files.lines(Path.of("f:/MyInfo.txt"))
.flatMap(line->Arrays.stream(line.split(","))
.map(item->new String[]{item}))
.toArray(String[][]::new);
} catch (IOException ioe) {
ioe.printStackTrace();
}
if (array != null) {
System.out.println(Arrays.deepToString(array));
}
prints
[[A6], [A7], [F2], [F3], [F6], [G6]]
Here is an approach similar to yours.
List<String[]> list = new ArrayList<>();
try {
Scanner scanner = new Scanner(new File("f:/MyInfo.txt"));
while (scanner.hasNextLine()) {
String[] arr = scanner.nextLine().split(",");
for (String item : arr) {
list.add(new String[]{item});
}
}
} catch (IOException ioe) {
ioe.printStackTrace();
}
There is no deepToString for Lists so you either iterate it or convert to a 2D array.
String[][] ar = list.toArray(String[][]::new);
System.out.println(Arrays.deepToString(ar));
prints
[[A6], [A7], [F2], [F3], [F6], [G6]]

i think you have to double the rows size and for each line just put one element and increment the i++

The declaration of the result array is not correct.
Since you want the end result should look like this, [[A6],[A7],[F2],[F3],[F6],[G6]], it is a 2-dimensional array with one row and six columns.
Considering it, I have changed and simplified your code.
int rows = 3;
String[][] r = new String[1][rows * 2];
FileInputStream fstream = new FileInputStream("/path/to/the/file")
BufferedReader br = new BufferedReader(new InputStreamReader(stream));
while((line = br.readLine()) != null) {
String[] current = line.split(",");
r[0][i++] = current[0];
r[0][i++] = current[1];
}

BufferedReader saving sentence, String array, then 2D int array

I have a .txt file that contains text that I would like to save part of it in a String, part of it in a String array, and then the last part in a 2D int array, and am faced with two issues:
How to read and save both of the arrays when their size is not known ahead of time?
2D array is not reading/saving properly
Here is the text file for reference:
This is the sentence to be read.
This
is
a
String
array.
90 47 110 95 95
101 87
54 0 38 12
Here is part of my method that is supposed to read and save the three data types:
BufferedReader br = new BufferedReader(new FileReader(fileName));
sentence = br.readLine();
stringArr = new String[5]; //how to initialize without set number of elements?
for(int i = 0; i<stringArr.length; i++){
stringArr[i] = br.readLine();
}
int2DArr = new int[3][5]; //how to initialize with any amount of rows and columns?
for(int i = 0; i<int2DArr.length; i++){
for(int j = 0; j<int2DArr[i].length; j++){
int2DArr[i][j] = br.read();
//how to read the space after each int ?
}
}
How would I "grab" the size of the arrays by reading the text file, so that when I initialize both arrays, I have the proper sizes? Any help would be greatly appreciated!

Instead of trying to achieve everything in a single pass we can pass through the file twice and obtain a neater code.
It will consume double time of course but it is going to help you understand how you could break bigger problems into smaller ones and deal with them one by one.
Here are the steps:
Determine size of stringArr and intArr in first pass
Fill value in respective array in second pass
If you are wondering how no of columns for int2DArr is determine. Simply we don't do it our self. We use the concept of Jagged Arrays
Read more here How do I create a jagged 2d array in Java?
import java.util.*;
import java.io.*;
class ReadFileIntoArr {
public static void main(String args[]) throws IOException {
String fileName = "test.txt";
BufferedReader br = new BufferedReader(new FileReader(fileName));
String line = br.readLine();
int strSize = 0;
int intSize = 0;
boolean isDigit = false;
while (line != null && line.trim().length() != 0) {
if (!isDigit && Character.isDigit(line.charAt(0)))
isDigit = true;
if (isDigit)
intSize++;
else
strSize++;
line = br.readLine();
}
br = new BufferedReader(new FileReader(fileName));
String[] stringArr = new String[strSize];
for (int i = 0; i < stringArr.length; i++)
stringArr[i] = br.readLine();
int[][] int2DArr = new int[intSize][];
for (int i = 0; i < int2DArr.length; i++)
int2DArr[i] = Arrays.stream(br.readLine().split(" ")).mapToInt(Integer::parseInt).toArray();
System.out.println(Arrays.toString(stringArr));
System.out.println(Arrays.deepToString(int2DArr));
}
}
Note: In single pass this could be accomplished with the help of ArrayList and later transfer everything into respective array.
Update: After understanding the constraints for your problem here is another version
import java.util.*;
import java.io.*;
class ReadFileIntoArr {
public static void main(String args[]) throws IOException {
String fileName = "test.txt";
BufferedReader br = new BufferedReader(new FileReader(fileName));
String line = br.readLine();
int strSize = 0;
int intSize = 0;
boolean isDigit = false;
while (line != null && line.trim().length() != 0) {
if (!isDigit && isDigit(line.charAt(0)))
isDigit = true;
if (isDigit)
intSize++;
else
strSize++;
line = br.readLine();
}
br = new BufferedReader(new FileReader(fileName));
String[] stringArr = new String[strSize];
for (int i = 0; i < stringArr.length; i++)
stringArr[i] = br.readLine();
int[][] int2DArr = new int[intSize][];
for (int i = 0; i < int2DArr.length; i++)
int2DArr[i] = convertStringArrToIntArr(br.readLine().split(" "));
System.out.println(Arrays.toString(stringArr));
System.out.println(Arrays.deepToString(int2DArr));
}
public static boolean isDigit(char c) {
return c >= '0' && c <= '9';
}
public static int[] convertStringArrToIntArr(String[] strArr) {
int[] intArr = new int[strArr.length];
for (int i = 0; i < strArr.length; i++)
intArr[i] = Integer.parseInt(strArr[i]);
return intArr;
}
}

Path path = Paths.get(fileName);
List<String> lines = Files.readAllLines(path, Charset.defaultCharset());
String title = lines.get(0);
List<String> words = new ArrayList<>();
for (int i = 1; i < lines.size(); ++i) {
String word = lines.get(i);
if (!word.isEmpty() && Character.isDigit(word.codePointAt(0)) {
break;
}
words.add(word);
}
String[] wordArray = words.toArray(new String[]);
int i0 = 1 + words.size();
int n = lines.size() - i0;
int[][] numbers = new int[n][];
for (int i = i0; i < lines.size(); ++i) {
String[] values = lines.get(i).trim().split("\\s+");
int m = values.length;
int[] row = new int[m];
for (int j = 0; j < m; ++m) {
row[j] = Integer.parse(values[j]);
}
numbers[i - i0] = row;
}
Path is a generalisation of File, also URLs.
Files is a treasure trove of file functions.
One could do without dynamically sized List; one would need to test first,
but normally one would use a List anyhow.
String.split splits on one or more whitespace.

How to add doubles into a 2d array from a file (Java)?

All the examples that i have seen involve specifying the number of rows and columns at the start of the file but the method I'm working on reads a file with the following:
1.0 2.0
3.0 4.0
and using this data creates a 2d array and stores it without specifying the number of rows and columns.
Here's the code I have written:
public static double[][] readMatrixFrom(String file) throws FileNotFoundException {
Scanner input = new Scanner(new FileReader(file));
int rows =0;
int columns =0;
while(input.hasNextLine()){
String line = input.nextLine();
rows++;
columns = line.length();
}
double[][] d = new double[rows][columns]
return d;
}
I'm unsure of how to add these values now that I have created the 2d array. i tried this but got an InputMismatchException.
Scanner s1 = new Scanner(file);
double[][] d = new double[rows][columns]
for (int i= 0;i<rows;i++) {
for (int j= 0;i<rows;j++) {
d[i][j] = s1.nextDouble();
}
}

if you just want to use the basic arrays you can achieve it with something like
Scanner input = new Scanner(new FileReader(file));
int row=0;
int col =0;
String s="";
//count number of rows
while(input.hasNextLine()) {
row++;
s=input.nextLine();
}
//count number of columns
for(char c: s.toCharArray()) {
if(c==' ')
col++;
}
col++; // since columns is one greater than the number of spaces
//close the file
input.close();
// and open it again to start reading it from the begining
input = new Scanner(new FileReader(file));
//declare a new array
double[][] d = new double[row][col];
int rowNum=0;
while(input.hasNextLine()) {
for(int i=0; i< col; i++) {
d[rowNum][i]= input.nextDouble();
}
rowNum++;
}
However if you prefer to use java collection you can avoid reading the file again. Just store the strings in a list and iterate over the list to extract elements from it.

Based on your input, Your columns = line.length(); is returning 7 rather than 2 as it returns the String length.
Hence try calculating the no of columns in the row columns = line.split(" ").length;
Also while trying to read your input you were using index i for the 2nd for-loop. It should be like below,
for (int i= 0;i<rows;i++) {
for (int j= 0;j<columns;j++) {
d[i][j] = s1.nextDouble();
}
}

In order to work with arrays of unknown size you should read the data into a Collection (such as a List). However, Collection(s) only work with the wrapper-types; so you will need to copy the elements back into an array of double(s) if that is what you really need. Something like,
public static double[][] readMatrixFrom(String file) throws FileNotFoundException {
Scanner input = new Scanner(new FileReader(file));
List<List<Double>> al = new ArrayList<>();
while (input.hasNextLine()) {
String line = input.nextLine();
List<Double> ll = new ArrayList<>();
Scanner sc = new Scanner(line);
while (sc.hasNextDouble()) {
ll.add(sc.nextDouble());
}
al.add(ll);
}
double[][] d = new double[al.size()][];
for (int i = 0; i < al.size(); i++) {
List<Double> list = al.get(i);
d[i] = new double[list.size()];
for (int j = 0; j < d[i].length; j++) {
d[i][j] = list.get(j);
}
}
return d;
}
Which I tested by creating a file in my home folder with your contents and running it like so
public static void main(String[] args) {
String file = System.getProperty("user.home") + File.separator + "temp.txt";
try {
System.out.println(Arrays.deepToString(readMatrixFrom(file)));
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}
And I get (as I assume you wanted)
[[1.0, 2.0], [3.0, 4.0]]

Read lines of numbers from a file to a 2d array using a for loop

I want to read lines of numbers from a file. The code is as follows but the IDE shows NullPointerException runtime exception. Not sure what I am doing wrong.
//reading the contents of the file into an array
public static void readAndStoreNumbers() {
//initialising the new object
arr = new int[15][];
try {
//create file reader
File f = new File("E:\\Eclipse Projects\\triangle.txt");
BufferedReader br = new BufferedReader(new FileReader(f));
//read from file
String nums;
int index = 0;
while ((nums = br.readLine()) != null) {
String[] numbers = nums.split(" ");
//store the numbers into 'arr' after converting into integers
for (int i = 0; i < arr[index].length; i++) {
arr[index][i] = Integer.parseInt(numbers[i]);
}
index++;
}
} catch (IOException e) {
e.printStackTrace();
}
}

Your second dimension of arr is uninitialized, and you are invoking
arr[index].length

You could be running into an NPEX for two reasons.
You don't finish your definition of arr - it's not evident in your code that you declare arr as int arr[][];
Even if you had the above, you wouldn't have set aside space for your second array. What you have now is a jagged array; you can have elements of whatever length in the second dimension you wish in your second array.
The only modification I made to your code to get it to work would be the following line:
arr[index] = new int[numbers.length];
...after pulling elements into numbers, and before entering the loop.

you need to change -
for(int i=0; i<arr[index].length; i++) {
to
arr[index] = new int[numbers.length];
for (int i = 0; i < numbers.length; i++) {

Java doesn't have real multidimensional arrays. What you are using is actually an array of int arrays: new int[n][] actually creates an array with room for n objects of type int[].
Consequently you will have to initialize each of those int arrays separately. That would have been obvious from the fact that you never actually specified the length of the second dimension anywhere in your program.

I think you should use StringBuilder..
//reading the contents of the file into an array
public static void readAndStoreNumbers() {
//initialising the StringBuffer
StringBuilder sb = new StringBuilder();
try {
//create file reader
File f = new File("E:\\Eclipse Projects\\triangle.txt");
BufferedReader br = new BufferedReader(new FileReader(f));
//read from file
String nums;
int index = 0;
while ((nums = br.readLine()) != null) {
String[] numbers = nums.split(" ");
//store the numbers into 'arr' after converting into integers
for (int i = 0; i < arr[index].length; i++) {
sb.append(Integer.parseInt(numbers[i])).append("\n");
}
}
} catch (IOException e) {
e.printStackTrace();
}
}

java regular expression getting values from a txt file [duplicate]

I am new to Java. I have one text file with below content.
`trace` -
structure(
list(
"a" = structure(c(0.748701,0.243802,0.227221,0.752231,0.261118,0.263976,1.19737,0.22047,0.222584,0.835411)),
"b" = structure(c(1.4019,0.486955,-0.127144,0.642778,0.379787,-0.105249,1.0063,0.613083,-0.165703,0.695775))
)
)
Now what I want is, I need to get "a" and "b" as two different array list.

You need to read the file line by line. It is done with a BufferedReader like this :
try {
FileInputStream fstream = new FileInputStream("input.txt");
BufferedReader br = new BufferedReader(new InputStreamReader(fstream));
String strLine;
int lineNumber = 0;
double [] a = null;
double [] b = null;
// Read File Line By Line
while ((strLine = br.readLine()) != null) {
lineNumber++;
if( lineNumber == 4 ){
a = getDoubleArray(strLine);
}else if( lineNumber == 5 ){
b = getDoubleArray(strLine);
}
}
// Close the input stream
in.close();
//print the contents of a
for(int i = 0; i < a.length; i++){
System.out.println("a["+i+"] = "+a[i]);
}
} catch (Exception e) {// Catch exception if any
System.err.println("Error: " + e.getMessage());
}
Assuming your "a" and"b" are on the fourth and fifth line of the file, you need to call a method when these lines are met that will return an array of double :
private static double[] getDoubleArray(String strLine) {
double[] a;
String[] split = strLine.split("[,)]"); //split the line at the ',' and ')' characters
a = new double[split.length-1];
for(int i = 0; i < a.length; i++){
a[i] = Double.parseDouble(split[i+1]); //get the double value of the String
}
return a;
}
Hope this helps. I would still highly recommend reading the Java I/O and String tutorials.

You can play with split. First find the line in the text that matches "a" (or "b"). Then do something like this:
Array[] first= line.split("("); //first[2] will contain the values
Then:
Array[] arrayList = first[2].split(",");
You will have the numbers in arrayList[]. Be carefull with the final brackets )), because they have a "," right after. But that is code depuration and it is your mission. I gave you the idea.