Develop Reference

How do I store the CSV file data into an array in Java?

Here is the CSV file I am using:
B00123,55
B00783,35
B00898,67
I need to read and store the first value entered in the file e.g. B00123 and store it into an array. A user can add to the file so it is not a fixed number of records.
So far, I have tried this code:
public class ArrayReader
{
static String xStrPath;
static double[][] myArray;
static void setUpMyCSVArray()
{
myArray = new double [4][5];
Scanner scanIn = null;
int Rowc = 0;
int Row = 0;
int Colc = 0;
int Col = 0;
String InputLine = "";
double xnum = 0;
String xfileLocation;
xfileLocation = "src\\marks.txt";
System.out.println("\n****** Setup Array ******");
try
{
//setup a scanner
/*file reader uses xfileLocation data, BufferedRader uses
file reader data and Scanner uses BufferedReader data*/
scanIn = new Scanner(new BufferedReader(new FileReader(xfileLocation)));
while (scanIn.hasNext())
{
//read line form file
InputLine = scanIn.nextLine();
//split the Inputline into an array at the comas
String[] InArray = InputLine.split(",");
//copy the content of the inArray to the myArray
for (int x = 0; x < myArray.length; x++)
{
myArray[Rowc][x] = Double.parseDouble(InArray[x]);
}
//Increment the row in the Array
Rowc++;
}
}
catch(Exception e)
{
}
printMyArray();
}
static void printMyArray()
{
//print the array
for (int Rowc = 0; Rowc < 1; Rowc++)
{
for (int Colc = 0; Colc < 5; Colc++)
{
System.out.println(myArray[Rowc][Colc] + " ");
}
System.out.println();
}
return;
}
public static void main(String[] args)
{
setUpMyCSVArray();
}
}
This loops round the file but doesn't not populate the array with any data. The outcome is:
****** Setup Array ******
[[D#42a57993
0.0
0.0
0.0
0.0
0.0

There is actually a NumberFormatException happening when in the first row when trying to convert the ID to Double. So I revised the program and it works for me.
import java.io.BufferedReader;
import java.io.FileReader;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;
public class ArrayReader
{
static String xStrPath;
static Map<String,Double> myArray = new HashMap<>();
static void setUpMyCSVArray()
{
Scanner scanIn = null;
int Rowc = 0;
int Row = 0;
int Colc = 0;
int Col = 0;
String InputLine = "";
double xnum = 0;
String xfileLocation;
xfileLocation = "/Users/admin/Downloads/mark.txt";
System.out.println("\n****** Setup Array ******");
try
{
//setup a scanner
/*file reader uses xfileLocation data, BufferedRader uses
file reader data and Scanner uses BufferedReader data*/
scanIn = new Scanner(new BufferedReader(new FileReader(xfileLocation)));
while (scanIn.hasNext())
{
//read line form file
InputLine = scanIn.nextLine();
//split the Inputline into an array at the comas
String[] inArray = InputLine.split(",");
//copy the content of the inArray to the myArray
myArray.put(inArray[0], Double.valueOf(inArray[1]));
//Increment the row in the Array
Rowc++;
}
}
catch(Exception e)
{
System.out.println(e);
}
printMyArray();
}
static void printMyArray()
{
//print the array
for (String key : myArray.keySet()) {
System.out.println(key + " = " + myArray.get(key));
}
return;
}
public static void main(String[] args)
{
setUpMyCSVArray();
}
}
Output:

the code can't reader anything ,you file path incorrect.give it absoulte file path.
scanIn = new Scanner(new BufferedReader(new FileReader(xfileLocation)));

I use opencsv library to read from csv.
import com.opencsv.CSVReader;
public class CSV {
private static String file = <filepath>;
private static List<String> list = new ArrayList<>();
public static void main(String[] args) throws Exception {
try {
CSVReader reader = new CSVReader(new FileReader(file));
String[] line;
while ((line = reader.readNext()) != null) {
list.add(line[0]);
}
Object[] myArray = list.toArray();
System.out.println(myArray.length);
System.out.println(myArray[0]);
} catch (Exception e) {
e.printStackTrace();
}
}
}
Output printed as below
3
B00123

Converting lines of text from a file to String Array

I read the information in a .txt file and now I would like to store the lines of information from the text into a String Array or a variable.
The information in the .txt file is as given:
Onesimus, Andrea
BAYV
Twendi, Meghan
RHHS
Threesten, Heidi
MDHS
I want to store BAYV, RHHS, MDHS into a different array from the names.
import java.io.File;
import java.util.Scanner;
class testing2 {
public static void main(String [] args) throws Exception {
File Bayviewcamp = new File ("H:\\Profile\\Desktop\\ICS3U\\Bayviewland Camp\\Studentinfo.txt");
Scanner scanner = new Scanner (Bayviewcamp);
while (scanner.hasNextLine())
System.out.println(scanner.nextLine());

Check whether names matches with the regex "[A-Z]+"
List<String> upperCaseList = new ArrayList<>();
List<String> lowerCaseList = new ArrayList<>();
while (scanner.hasNextLine()) {
String[] names = scanner.nextLine().split(",");
for(String name:names) {
if(name.matches("[A-Z]+")) {
upperCaseList.add(name);
}
else {
lowerCaseList.add(name);
}
}
}
As per your example, some of the names has leading spaces. you may have to trim those spaces before you compare with the regex
for(String name:names) {
if(name.trim().matches("[A-Z]+")) {
upperCaseList.add(name.trim());
}
else {
lowerCaseList.add(name.trim());
}
}

Below code has few restrictions like:
There must be format that you said (name and next line value)
Array size is 100 by default but you can change as you want
By name I mean one line: (Onesimus, Andrea) it's under first index in names array.
private static final int ARRAY_LENGTH = 100;
public static void main(String[] args) throws FileNotFoundException {
boolean isValue = false;
File txt = new File("file.txt");
Scanner scanner = new Scanner(txt);
String[] names = new String[ARRAY_LENGTH];
String[] values = new String[ARRAY_LENGTH];
int lineNumber = 0;
while (scanner.hasNextLine()) {
if (isValue) {
values[lineNumber / 2] = scanner.nextLine();
} else {
names[lineNumber / 2] = scanner.nextLine();
}
isValue = !isValue;
lineNumber++;
}
for (int i = 0; i < ARRAY_LENGTH; i++) {
System.out.println(names[i]);
System.out.println(values[i]);
}
}
Below code return separated names:
private static final int ARRAY_LENGTH = 100;
public static void main(String[] args) throws FileNotFoundException {
boolean isValue = false;
File txt = new File("file.txt");
Scanner scanner = new Scanner(txt);
String[] names = new String[ARRAY_LENGTH];
String[] values = new String[ARRAY_LENGTH];
int namesNumber = 0;
int valuesNumber = 0;
while (scanner.hasNextLine()) {
if (!isValue) {
String tempArrayNames[] = scanner.nextLine().split(",");
values[valuesNumber++] = tempArrayNames[0].trim();
values[valuesNumber++] = tempArrayNames[1].trim();
} else {
names[namesNumber++] = scanner.nextLine();
}
isValue = !isValue;
}
}

How to store string values in string array?

I wanted to store name values in String a[] = new String[3];
public static void main(String[] args) throws IOException {
BufferedReader bo = new BufferedReader(new InputStreamReader(System.in));
String name = bo.readLine();
String a[] = new String[3];
}
}

I guess this should suffice:
String a[] = new String[3];
for(int i=0; i<a.length;i++) {
String name = bo.readLine();
a[i] = name;
}

If your name represents names separated by space, try this:
String a[] = name.split(" ");

If you're working from the console I think this is the easiest way for a beginner to tackle user input:
import java.util.Scanner;
public class ReadToStringArray {
private static String[] stringArray = new String[3];
// method that reads user input into the String array
private static void readToArray() {
Scanner scanIn = new Scanner(System.in);
// read from the console 3 times
for (int i = 0; i < stringArray.length; i++) {
System.out.print("Enter a string to put at position " + i + " of the array: ");
stringArray[i] = scanIn.nextLine();
}
scanIn.close();
System.out.println();
}
public static void main(String[] args) {
readToArray();
// print out the stringArray contents
for (int i = 0; i < stringArray.length; i++) {
System.out.println("String at position " + i + " of the array: " + stringArray[i]);
}
}
}
This method uses the java's native Scanner class. You can just copy and paste this and it will work.

Trying to read a file and put values in an array

I need to read certain portions of a file and put them into their correct array.
public static void load(String fileName, String[] itemNumbers,
String[] itemNames, double[] priceOfItem, int[] quantity) throws IOException{
int i = 0;
File inFile = new File(fileName);
Scanner reader = new Scanner(inFile);
while(reader.hasNext()){
itemNumbers[i] = reader.next();
itemNames[i] = reader.next();
priceOfItem[i] = reader.nextDouble();
quantity[i] = reader.nextInt();
i++;
}
//This is just to see if it worked
System.out.println(itemNumbers[i]);
System.out.println(itemNames[i]);
System.out.println(priceOfItem[i]);
System.out.println(quantity[i]);
}
Here is the file I'm reading.
E3233 CordlessDrill 129.99 12
W2321 WindowSealer 3.39 84
The arrays are in order with the file portions.
When I run this I receive the following
null
null
0.0
0

Make sure it says
while(reader.hasNextLine())

have you tried using FileReader?
public static void load(String fileName, String[] itemNumbers,
String[] itemNames, double[] priceOfItem, int[] quantity) throws IOException{
File inFile = new File(fileName);
char[] cbuf = new char[(int) inFile.length()];
FileReader r = new FileReader(inFile);
r.read(cbuf);
String finalString = String.valueOf(cbuf);
String[] lines = finalString.split("\n");
itemNumbers = new String[lines.length];
itemNames = new String[lines.length];
priceOfItem = new double[lines.length];
quantity = new int[lines.length];
for(int i = 0; i < lines.length; i++){
String line = lines[i].replace("\n", "");
String[] values = line.split(" ");
String itemNumber = values[0];
String itemName = values[1];
double price = Double.parseDouble(values[2]);
int quant = Integer.parseInt(values[3].replace(String.valueOf((char)13), "").replace(" ", "").replace("\"", ""));
itemNumbers[i] = itemNumber;
itemNames[i] = itemName;
priceOfItem[i] = price;
quantity[i] = quant;
}
r.close();
for(int i = 0; i < itemNames.length; i++){
System.out.println(itemNumbers[i]);
System.out.println(itemNames[i]);
System.out.println(priceOfItem[i]);
System.out.println(quantity[i]);
System.out.println("\n");
}
}
this method relies on using spaces in your file, I would add comma's and end lines with semicolons to be safe, but if you maintain the same format this should work.

JAVA Filling a 2D array from a file with an unknown amount of rows

I am trying to figure out how to make a program that reads data from a text file, and fills a Jtable with it, I will need to be able to search the table, and do some calculations with the numbers.
A row in the text file would contain:
name, country, gender, age, weight
The number of rows is unknown (I need to count the number of rows).
This is what I tried, but it seems to crash. I need to count the # of rows, and then fill the array with the content from the rows.
package Jone;
import java.io.*;
import java.util.*;
public class Jone {
public static void main (String [] args)throws IOException{
int rows = 0;
Scanner file = new Scanner (new File("data.txt"));
while (file.hasNextLine()){rows++;}
Object[][] data = new Object[rows][5];
System.out.print(rows);
file.nextLine();
for(int i = 0;i<rows;i++)
{
String str = file.nextLine();
String[] tokens= str.split(",");
for (int j = 0;j<5;j++)
{
data[i][j] = tokens[j];
System.out.print(data[i][j]);
System.out.print(" ");
}
}
file.close();
}
}

change your code as follows
package Jone;
import java.io.*;
import java.util.*;
public class Jone {
public static void main (String [] args)throws IOException{
try{
int rows = 0;
Scanner file = new Scanner (new File("data.txt"));
while (file.hasNextLine())
{
rows++;
file.nextLine();
}
file = new Scanner (new File("data.txt"));
System.out.println(rows);
Object[][] data = new Object[rows][5];
for(int i = 0;i<rows;i++)
{
String str = file.nextLine();
String[] tokens= str.split(",");
for (int j = 0;j<5;j++)
{
data[i][j] = tokens[j];
System.out.print(data[i][j]);
System.out.print(" ");
}
}
file.close();
}
catch(Exception e)
{
e.printStackTrace();
}
}

You create an array with 0 rows and then you try to access the empty array dimension.
Also I suppose you should reset the pointer of the scanner after counting the rows.
ArrayList should be more useful for your goal.

class Person {
String name, country, gender;
int age;
double weight;
public Person(String n, String c, String g, int a, double w) {
name = n;
country = c;
gender = g;
age = a;
weight = w;
}
}
Would properly model your data better when you are extracting from the file (I took a guess at Person but call it what you will). We then use ArrayList like so:
public static void main (String[] args) throws IOException {
ArrayList<Person> people = new ArrayList<Person>();
Scanner file = new Scanner (new File("data.txt"));
while (file.hasNextLine()) {
String str = file.nextLine();
String[] tokens= str.split(",");
people.add(new Person(tokens[0], tokens[1], tokens[2],
Integer.parseInt(tokens[3], Double.parseDouble(tokens[4]))));
}
file.close();
Person[] arrayPeople = people.toArray();
}
ArrayLists are far more powerful than arrays as you can perform all sorts of operations on them like sorts and searches and of course you don't have to worry about their initial size because they just grow as you add new elements.

Maroun is right, you really need to use some Collections to help you with that :
public static void main(String[] args) throws Exception {
List<String[]> lines = readFiles(new File("data.txt"));
String[][] data = lines.toArray(new String[0][]);
}
public static List<String[]> readFiles(File file) {
List<String[]> data = new LinkedList<>();
Scanner scanner = null;
try {
scanner = new Scanner(file);
while (scanner.hasNextLine()) {
String line = scanner.nextLine();
String[] tokens = line.split(",");
data.add(tokens);
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} finally {
scanner.close();
}
return data;
}
Note that you can use some third party libraries like Commons IO to read the file's lines :
List<String> lines = org.apache.commons.io.FileUtils.readLines(new File("data.txt"));)
Less code = less bugs!
Hope it helps

Move this line
Object[][] data = new Object[rows][5];
below
System.out.print(rows);
But as per answers above, we suggest change the code to use array lists if possible.