We Keep Coding

Creating an array from a matrix input

I have an input file which is in the form of a matrix:
I want to turn this input from a file into an array. I am not sure how to go about it.Any suggestions? I've tried the code below but when I compile the code and pass the file as an input I am returned with nothing.
public static void main(String[]args)
{
int size;
Scanner entry = new Scanner(System.in);
int myMatrix[][] = new int[0][0];
try
{
size = entry.nextInt();
myMatrix = new int[size][size];
for (int i=0; i<size; i++)
{
for (int j = 0; j<size; j++)
{
myMatrix[i][j] = entry.nextInt();
}
}
for (int i = 0; i < size; i++) {
for (int j = 0; j < size; j++)
System.out.print(myMatrix[i][j] + " ");
System.out.println();
}
}
catch (Exception e)
{
}
finally
{
entry.close();
}

Change (System.in) to: (new File("filename.txt"))
Here's more info on reading from text files:
https://www.w3schools.com/java/java_files_read.asp

You can use Files.lines to read all the lines from a file.
String filePath = entry.nextLine();
int[][] myMatrix = Files.lines(Paths.get(filePath))
.map(l -> Arrays.stream(l.split(" ")).mapToInt(Integer::parseInt).toArray())
.toArray(int[][]::new);

Java read file and write into array

--------------- SOLVED !!! -----------------------
I would like to thank you, everyone, for your help !
I have to read a file where I have nxm elements, and then put those elements into 2D array, and then print it out. I'm a little bit stuck at printing my array out. In file.txt I have 2x2 => 2 lines and 2 columns, and elements are:1 2 3 4.
Here is my code:
public class ex_1
{
public static void main(String args[])
{
FileReader fr = new FileReader("FirstMatrix.txt");
BufferedReader br = new BufferedReader(fr);
String s = br.readLine();
String[] split = s.split("x");
int k=Integer.parseInt(split[0]);
int l=Integer.parseInt(split[1]);
System.out.println("Matrix dimensions: "+k+" lines, "+l+" columns si "+k*l+" elements");
System.out.print("Elements in matrix are: \n");
int[][] FirstMatrix = new int [k][l];
while ((s = br.readLine()) != null)
{
for(int i=0; i<FirstMatrix.length; i++)
for(int j=0; j<FirstMatrix[i].length;j++)
{
FirstMatrix[i][j] = Integer.parseInt(s);
System.out.println("FirstMatrix["+i+"]["+j+"]="+FirstMatrix[i][j]);
}
}
br.close();
My output, how it is:
FirstMatrix[0][0]=1
FirstMatrix[0][1]=1
FirstMatrix[1][0]=1
FirstMatrix[1][1]=1
FirstMatrix[0][0]=2
FirstMatrix[0][1]=2
FirstMatrix[1][0]=2
FirstMatrix[1][1]=2
FirstMatrix[0][0]=3
FirstMatrix[0][1]=3
FirstMatrix[1][0]=3
FirstMatrix[1][1]=3
FirstMatrix[0][0]=4
FirstMatrix[0][1]=4
FirstMatrix[1][0]=4
FirstMatrix[1][1]=4
How I want it to be:
FirstMatrix[0][0]=1
FirstMatrix[0][1]=2
FirstMatrix[1][0]=3
FirstMatrix[1][1]=4
Does anyone know how I can fix this print out please?
EDIT!!
If I change code like this
int[][] FirstMatrix = new int [k][l];
while ((s = br.readLine()) != null)
{
for(int i=0; i<k;i++)
for(int j=0; j<l; j++)
{
FirstMatrix[i][j] = Integer.parseInt(s);
}
}
br.close();
for(int i=0; i<FirstMatrix.length; i++)
for(int j=0; j<FirstMatrix[i].length;j++)
{
System.out.println("FirstMatrix["+i+"]["+j+"]="+FirstMatrix[i][j]);
}
I get this output:
FirstMatrix[0][0]=4
FirstMatrix[0][1]=4
FirstMatrix[1][0]=4
FirstMatrix[1][1]=4

You're doing n*n times the loop. Because everytime that you read the file are entering the loop. If you know that every line is a number, you could read only one time and print each row.
Try it and let me know what happen.
Best regards from Mexico

After this line System.out.print("Elements in matrix are: \n");
paste this code.
int[][] FirstMatrix = new int [l][k];
for(int j=0; j<l;j++)
{
for(int i=0; i<k; i++) {
s = br.readLine());
FirstMatrix[j][i] = Integer.parseInt(s);
System.out.println("FirstMatrix["+j+"]["+i+"]="+FirstMatrix[j][i]);
}
}
Don't use while loop.

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
public class ex_1 {
public static void main(String args[]) throws IOException {
FileReader fr = new FileReader("FirstMatrix.txt");
BufferedReader br = new BufferedReader(fr);
String s = br.readLine();
String[] split = s.split("x");
int k = Integer.parseInt(split[0]);
int l = Integer.parseInt(split[1]);
System.out.println("Matrix dimensions: " + k + " lines, " + l + " columns si " + k * l + " elements");
System.out.print("Elements in matrix are: \n");
int[][] FirstMatrix = new int[k][l];
for (int lineIndex = 0; lineIndex < k; lineIndex++) {
for (int columnIndex = 0; columnIndex < l; columnIndex++) {
s = br.readLine();
FirstMatrix[lineIndex][columnIndex] = Integer.valueOf(s);
}
}
for (int a = 0; a < k; a++) {
for (int b = 0; b < l; b++)
System.out.print(FirstMatrix[a][b] + " ");
System.out.println();
}
br.close();
}
}

Searching in arraylist<String[]> from user input

I want to search in an arraylist from a user input but my if condition doesn't seem to work. Using boolean and .contains() doesn't work for my programme either. This is the coding:
String phone;
phone=this.text1.getText();
System.out.println("this is the phone: " + phone);
BufferedReader line = new BufferedReader(new FileReader(new File("C:\\Users\\Laura Sutardja\\Documents\\IB DP\\Computer Science HL\\cs\\data.txt")));
String indata;
ArrayList<String[]> dataArr = new ArrayList<String[]>();
while ((indata = line.readLine()) != null) {
String[] club = new String[2];
String[] value = indata.split(",", 2);
//for (int i = 0; i < 2; i++) {
int n = Math.min(value.length, club.length);
for (int i = 0; i < n; i++) {
club[i] = value[i];
}
boolean aa = dataArr.contains(this.text1.getText());
if(aa==true)
text2.setText("The data is found.");
else
text2.setText("The data is not found.");
dataArr.add(club);
}
for (int i = 0; i < dataArr.size(); i++) {
for (int x = 0; x < dataArr.get(i).length; x++) {
System.out.printf("dataArr[%d][%d]: ", i, x);
System.out.println(dataArr.get(i)[x]);
}
}
}
catch ( IOException iox )
{
System.out.println("Error");
}

Your dataArr is a list of String[], and you are searching for a String. The two are different kind of objects.
I don't really know how the content of the club array looks like, but you should either change dataArr in order to hold plain String, or to write a method which looks iteratively in dataArr for a String[] containing the output of this.text1.getText().

There is a lot wrong with the program. I assume you want to read a textfile and store each line in the arraylist. To do this you have to split each line of the textfile and store that array in the arrayList.
String[] value;
while ((indata = line.readLine()) != null) {
value = indata.split(",");
dataArr.add(value);
}
Now you have the contents of the file in the arrayList.
Next you want to compare the userinput with each element of the arraylist.
int j = 0;
for (int i = 0; i < dataArr.size(); i++) {
String[] phoneData = dataArr.get(i);
if (phoneData[1].equals(phone)) { // i am assuming here that the phone number is the 2nd element of the String[] array, since i dont know how the textfile looks.
System.out.println("Found number.");
club[j++] = phoneData[1];
} else if (i == dataArr.size()-1) {
System.out.println("Didn't find number.");
}
}
Edit:
As requested:
String phone;
phone = "38495";
System.out.println("this is the phone: " + phone);
BufferedReader line = new BufferedReader(new FileReader(new File("list.txt")));
String indata;
ArrayList<String[]> dataArr = new ArrayList<>();
String[] club = new String[2];
String[] value;// = indata.split(",", 2);
while ((indata = line.readLine()) != null) {
value = indata.split(",");
dataArr.add(value);
}
int j = 0;
for (int i = 0; i < dataArr.size(); i++) {
String[] phoneData = dataArr.get(i);
if (phoneData[1].equals(phone)) {
System.out.println("Found number.");
club[j++] = phoneData[1];
break;
} else if (i == dataArr.size()-1) {
System.out.println("Didn't find number.");
}
}
I hope this makes sense now.

Array throws NullPointerException in Java

I have the following little problem... I have this code that uses the method OpenFile() of one class ReadData to read a .txt file and also I have another class ArraysTZones used to create an object that stores 3 arrays (data1,data2,data3) and 3 integers (total1,total2,total3) returned by the method OpenFile(). The problem is that when I try to display each array (data1,data2,data3) using the method getArray() of ArrayTZones it stops and displays the error NullPointerException. Anyone knows how could I fix this?
public static void main (String args[]) throws IOException {
String fileName = ".//data.txt";
int[] def = new int[180];
try {
ReadData file = new ReadData(fileName);
ArraysTZones summaryatz = new ArraysTZones();
summaryatz = file.OpenFile();
for (int i = 0; i < 180; i++)
System.out.print (summaryatz.getArray1()[i] + " ");
System.out.println ("");
System.out.println (summaryatz.getTotal1());
for (int i = 0; i < 180; i++)
System.out.print (summaryatz.getArray2()[i] + " ");
System.out.println ("");
System.out.println (summaryatz.getTotal2());
for (int i = 0; i < 180; i++)
System.out.print (summaryatz.getArray3()[i] + " ");
System.out.println ("");
System.out.println (summaryatz.getTotal3());
}
catch (IOException e) {
System.out.println(e.getMessage());
}
}
Heres OpenFile()
public ArraysTZones OpenFile() throws IOException {
FileReader reader = new FileReader(path);
BufferedReader textReader = new BufferedReader(reader);
int numberOfTimeZones = 3;
int[] data1 = new int[180];
int[] data2 = new int[180];
int[] data3 = new int[180];
int total1 = 0;
int total2 = 0;
int total3 = 0;
ArraysTZones atz = new ArraysTZones();
for (int i = 0; i < numberOfTimeZones; i++){
if (i == 0) {
String firstTimeZone = textReader.readLine();
String[] val = firstTimeZone.split ("\\s+");
for (int u = 0; u < val.length; u++)
{
int stats = (int)(Math.ceil(Math.abs(Double.parseDouble(val[u]))));
total1 += stats;
data1[u] = stats;
}
total1= total1/180;
atz.setTotal1(total1);
atz.setArray1(data1);
}
else
if (i == 1) {
String secondTimeZone = textReader.readLine();
String[] val = secondTimeZone.split ("\\s+");
for (int u = 0; u < val.length; u++)
{
int stats = (int)(Math.ceil(Math.abs(Double.parseDouble(val[u]))));
total2 += stats;
data2[u] = stats;
}
total2= total2/180;
atz.setTotal2(total2);
atz.setArray2(data2);
}
else {
String thirdTimeZone = textReader.readLine();
String[] val = thirdTimeZone.split ("\\s+");
for (int u = 0; u < val.length; u++)
{
int stats = (int)(Math.ceil(Math.abs(Double.parseDouble(val[u]))));
total3 += stats;
data3[u] = stats;
}
total3= total3/180;
atz.setTotal3(total3);
atz.setArray3(data3);
}
}
textReader.close();
return atz;
}
The getArray()
public int[] getArray1 () {
return data1;
}
And setArray()
public void setArray1 (int[] farray) {
int[] data1 = new int[180];
//int[] farray = new int[180];
data1 = farray;
}

The problem seems to be here
public void setArray1 (int[] farray)
{
int[] data1 = new int[180];
//int[] farray = new int[180];
data1 = farray;
}
You're declaring a new variable called data1 and storing the content of farray to it.
After that method is done, that variable will be removed, due to his scope.
Remove int[] from the line int[] data1 = new int[180]; (or just remove the whole line .. it is unnecessary) and your data will be stored in the correct variable that was declared for the class.
public void setArray1 (int[] farray) {
data1 = farray;
}

You have to initialize ArraysTZones

Reading from file/array. No values. No errors

Any ideas what I am missing here? I am reading from a file array. The values in the text file don't get stored and there is no output. All I get is "names and totals" but no values.
I don't know.
private int[] totals;
private String[] names;
private String[] list;
private int count;
public void readData() throws IOException {
BufferedReader input = new BufferedReader(new FileReader("cookies.txt"));
//create the arrays
totals = new int[count];
names = new String[count];
list = new String[count];
//read in each pair of values
String quantityString = input.readLine();
for (int i = 0; i < count; i++) {
names[i] = input.readLine();
list[i] = input.readLine();
quantityString = input.readLine();
totals[i] = Integer.parseInt(quantityString);
}
}
public void display() {
System.out.println("names totals")
for (int i = 0; i < count; i++)
System.out.println(list[i] + " \t " + names[i] + " \t" + totals[i]);
}
//called to compute and print the result
public void printResults() {
//find the best teacher
int maxIndex = 0;
int maxValue = 0;
//for each record stores
for (int i = 0; i < count; i++) {
//if we have a new MAX value so far, update variables
if (maxValue < totals[i]) {
maxValue = totals[i];
maxIndex = i;
}
}
}

You never give the variable count a value, so it initialized to 0 by Java. This means that your arrays are of size 0 also.
So since count is zero, you never read anything from the file, which is why nothing is stored in your arrays and also why nothing is printed out.
Example: Reading a File line-by-line
// create temporary variable to hold what is being read from the file
String line = "";
// when you don't know how many things you have to read in use a List
// which will dynamically grow in size for you
List<String> names = new ArrayList<String>();
List<Integer> values = new ArrayList<Integer>();
// create a Reader, to read from a file
BufferedReader input = new BufferedReader(new FileReader("cookies.txt"));
// read a full line, this means if you line is 'Smith 36'
// you read both of these values together
while((line = input.readLine()) != null)
{
// break 'Smith 36' into an array ['Smith', '36']
String[] nameAndValue = line.split("\\s+");
names.add(nameAndValue[0]); // names.add('Smith')
values.add(Integer.parseInt(nameAndValue[1]); // values.add(36);
}