I've found a lot of similar questions on Stack Overflow so far, but none of them have actually answered my question. How do I read the data from different columns in a text file into three separate arrays?
Currently my BufferedReader is going through the entire text file and reading it line by line. The problem is, each line is stored as a singular array element.
As you can see, I tried to access the array elements by calling certain data from the "lines[]" array, which contains all of the lines in the file as separate elements. I just have no idea how to access those elements individually and then store them all in separate arrays. Below are the contents of the text file I'm reading from, and then the Java code itself.
(Name,Team,Score)
John,Blue,20
Jamie,White,28
Jonathan,Blue,19
Ron,White,39
Ron,Blue,29
--
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
public class Bowling7 {
public static void main(String[] args) {
try {
BufferedReader fin = new BufferedReader(new FileReader(new File("bowling.txt")));
System.out.println("File open successful!");
int line = 0;
String[] lines;
String[] names;
String[] teams;
int[] scores;
for (String x = fin.readLine(); x != null; x = fin.readLine()) {
lines = x.split(",");
teams[line] = lines[line];
scores[line] = lines[line];
line++;
}
System.out.println(lines[0]);
System.out.println(lines[1]);
catch (IOException e) {
System.out.println("File I/O error!");
}
}
}
Java arrays have a fixed length, your approach is off because you assume they are dynamic. Use a Collection, like List, and you can use Files.readAllLines(Path) to get all of the lines with one call. Remember to skip the first line (the header), and parse the score. Like,
File f = new File("bowling.txt");
try {
List<String> lines = Files.readAllLines(f.toPath());
List<String> names = new ArrayList<>();
List<String> teams = new ArrayList<>();
List<Integer> scores = new ArrayList<>();
for (String line : lines.subList(1, lines.size())) {
String[] tokens = line.split("\\s*,\\s*");
names.add(tokens[0]);
teams.add(tokens[1]);
scores.add(Integer.parseInt(tokens[2]));
}
System.out.println("Names: " + names);
System.out.println("Teams: " + teams);
System.out.println("Scores: " + scores);
} catch (IOException e) {
e.printStackTrace();
}
I get
Names: [John, Jamie, Jonathan, Ron, Ron]
Teams: [Blue, White, Blue, White, Blue]
Scores: [20, 28, 19, 39, 29]
Something like this would work
List<String> lines= Files.readAllLines(file.toPath());
String[] teams=new String[lines.size()],names=new String[lines.size()];
int[] scores=new int[lines.size()];
for (int i = 0; i < lines.size(); i++) {
String[] sections=lines.get(i).split(",");
names[i]=sections[0];
teams[i]=sections[1];
scores[i]= Integer.parseInt(sections[2]);
}
System.out.println(Arrays.toString(names));
System.out.println(Arrays.toString(teams));
System.out.println(Arrays.toString(scores));
Related
I am learning about all of the different ways to take input from a text file and read through the content. I am struggling to use a try - catch block (with resources), and reading in the file name.
Below is what I have written for this part so far:-
public static void main(String[] args)
{
ArrayList<StationRecord> data = new ArrayList<>();
String stationName = null;
Scanner scan = new Scanner(System.in);
System.out.println("What is the filename?");
String input = scan.nextLine();
File file = new File(input);
try(BufferedReader in = new BufferedReader(new FileReader(file))){
while(scan.hasNext()){
stationName = scan.nextLine();
int yearMonthDay = scan.nextInt();
int max = scan.nextInt();
int min = scan.nextInt();
int avg = scan.nextInt();
double dif = scan.nextDouble();
StationRecord sr = new StationRecord(yearMonthDay, max, min, avg, dif);
data.add(sr);
}
}
catch(IOException e)
{
e.printStackTrace();
}
catch(Exception e)
{
e.printStackTrace();
}
}
I am trying to do this for not only one file, but two of them. Regardless, here is a sample of input:-
Console: What is the filename?
TempData2018a.txt
After this is entered, I am trying to go through the data in the text file and add it to the ArrayList of type StationRecord (my other class).
Any suggestions and guidance would be much appreciated! Also any input on how you might do this with 2 files would be awesome!.
Edit: .txt file data example
PITTSBURGH ALLEGHENY CO AIRPORT PA
20180101 11 2 7 -22.614762
20180102 12 5 9 -20.514762
20180103 23 2 13 -16.414762
I am trying to store that whole first line in a variable called stationName. Then Im trying to store the next int, int, int, int double in an ArrayList of StationRecord type.
Since this is 2018, please stop using new File(..) and start using nio APIs. As you are using Java 8, you can easily achieve what you are trying to achieve here! So, you can create your StationRecord like this:
Path filePath = Paths.get(pathToFile);
String stationName = Files.lines(filePath)
.findFirst()
.get();
List<StationRecord> stationRecords =
Files.lines(filePath)
.skip(1) //Skip first line since it has station name
.map(line -> line.split("\\s")) // split at a space starting from 2nd line
.map(
stationData -> new StationRecord(Integer.valueOf(stationData[0]),
Integer.valueOf(stationData[1]), Integer.valueOf(stationData[2]),
Integer.valueOf(stationData[3]), Double.valueOf(stationData[4]))) // Create StationRecord object using the split fields
.collect(Collectors.toList()); // Collect result to an ArrayList
Using Java 7 & Java 8 API's feature, you can solve your problem like below:
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
public class LineOperation {
private static List<String> lines;
public static void main(String[] args) throws IOException {
lines = Collections.emptyList();
try {
lines = Files.readAllLines(Paths.get("C:\\Users\\Abhinav\\Downloads\\TempData2018a.txt"), StandardCharsets.UTF_8);
String stationName = lines.get(0);
String[] arr = null;
ArrayList<StationRecord> data = new ArrayList<>();
for(int i=1;i<lines.size();i++) {
arr = lines.get(i).split(" ");
data.add(new StationRecord(Long.parseLong(arr[0]), Integer.parseInt(arr[1]), Integer.parseInt(arr[2]), Integer.parseInt(arr[3]), Double.parseDouble(arr[4])));
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
But I strongly recommend you to refer below links for your further clarifications on Java I/O:-
Java – Read from File
Read a File into an ArrayList
As part of a project I'm working on, I'd like to clean up a file I generate of duplicate line entries. These duplicates often won't occur near each other, however. I came up with a method of doing so in Java (which basically find a duplicates in the file, I stored two strings in two arrayLists and iterating but it was not working because of nested for loops i am getting into the condition manyways.
I need an integrated solution for this, however. Preferably in Java. Any ideas?
List item
public class duplicates {
static BufferedReader reader = null;
static BufferedWriter writer = null;
static String currentLine;
public static void main(String[] args) throws IOException {
int count=0,linecount=0;;
String fe = null,fie = null,pe=null;
File file = new File("E:\\Book.txt");
ArrayList<String> list1=new ArrayList<String>();
ArrayList<String> list2=new ArrayList<String>();
reader = new BufferedReader(new FileReader(file));
while((currentLine = reader.readLine()) != null)
{
StringTokenizer st = new StringTokenizer(currentLine,"/"); //splits data into strings
while (st.hasMoreElements()) {
count++;
fe=(String) st.nextElement();
//System.out.print(fe+"/// ");
//System.out.println("count="+count);
if(count==1){ //stores 1st string
pe=fe;
// System.out.println("first element "+fe);
}
else if(count==5){
fie=fe; //stores 5th string
// System.out.println("fifth element "+fie);
}
}
count=0;
if(linecount>0){
for(String s1:list1)
{
for(String s2:list2){
if(pe.equals(s1)&&fie.equals(s2)){ //checking condition
System.out.println("duplicate found");
//System.out.println(s1+ " "+s2);
}
}
}
}
list1.add(pe);
list2.add(fie);
linecount++;
}
}
}
i/p:
/book1/_cwc/B737/customer/Special_Reports/
/Airbook/_cwc/A330-200/customer/02_Watchlists/
/book1/_cwc/B737/customer/Special_Reports/
/jangeer/_cwc/Crj_200/customer/plots/
/Airbook/_cwc/A330-200/customer/02_Watchlists/
/jangeer/_cwc/Crj_200/customer/06_Performance_Summaries/
/jangeer/_cwc/Crj_200/customer/02_Watchlists/
/jangeer/_cwc/Crj_200/customer/01_Highlights/
/jangeer/_cwc/ERJ170/customer/01_Highlights/
o/p:
/book1/_cwc/B737/customer/Special_Reports/
/Airbook/_cwc/A330-200/customer/02_Watchlists/
/jangeer/_cwc/Crj_200/customer/plots/
/jangeer/_cwc/Crj_200/customer/06_Performance_Summaries/
/jangeer/_cwc/Crj_200/customer/02_Watchlists/
/jangeer/_cwc/Crj_200/customer/01_Highlights/
Use a Set<String> instead of Arraylist<String>.
Duplicates aren't allowed in a Set, so if you just add everyline to it, then get them back out, you'll have all distinct strings.
Performance-wise it's also quicker than your nested for-loop.
public static void removeDups() {
String[] input = new String[] { //Lets say you read whole file in this string array
"/book1/_cwc/B737/customer/Special_Reports/",
"/Airbook/_cwc/A330-200/customer/02_Watchlists/",
"/book1/_cwc/B737/customer/Special_Reports/",
"/jangeer/_cwc/Crj_200/customer/plots/",
"/Airbook/_cwc/A330-200/customer/02_Watchlists/",
"/jangeer/_cwc/Crj_200/customer/06_Performance_Summaries/",
"/jangeer/_cwc/Crj_200/customer/02_Watchlists/",
"/jangeer/_cwc/Crj_200/customer/01_Highlights/",
"/jangeer/_cwc/ERJ170/customer/01_Highlights/"
};
ArrayList<String> outPut = new ArrayList<>(); //The array list for storing output i.e. distincts.
Arrays.stream(input).distinct().forEach(x -> outPut.add(x)); //using java 8 and stream you get distinct from input
outPut.forEach(System.out::println); //I will write back to the file, just for example I am printing out everything but you can write back the output to file using your own implementation.
}
The output when I ran this method was
/book1/_cwc/B737/customer/Special_Reports/
/Airbook/_cwc/A330-200/customer/02_Watchlists/
/jangeer/_cwc/Crj_200/customer/plots/
/jangeer/_cwc/Crj_200/customer/06_Performance_Summaries/
/jangeer/_cwc/Crj_200/customer/02_Watchlists/
/jangeer/_cwc/Crj_200/customer/01_Highlights/
/jangeer/_cwc/ERJ170/customer/01_Highlights/
EDIT
Non Java 8 answer
public static void removeDups() {
String[] input = new String[] {
"/book1/_cwc/B737/customer/Special_Reports/",
"/Airbook/_cwc/A330-200/customer/02_Watchlists/",
"/book1/_cwc/B737/customer/Special_Reports/",
"/jangeer/_cwc/Crj_200/customer/plots/",
"/Airbook/_cwc/A330-200/customer/02_Watchlists/",
"/jangeer/_cwc/Crj_200/customer/06_Performance_Summaries/",
"/jangeer/_cwc/Crj_200/customer/02_Watchlists/",
"/jangeer/_cwc/Crj_200/customer/01_Highlights/",
"/jangeer/_cwc/ERJ170/customer/01_Highlights/"
};
LinkedHashSet<String> output = new LinkedHashSet<String>(Arrays.asList(input)); //output is your set of unique strings in preserved order
}
I'm fairly new to programming and I recently wrote something to utilize a scanner class to fill an object array from a text file. Essentially, I can re-write this text file or add new info and won't have to change the code. I suppose my question is this: is there an easier/more preferred method to doing this? I'm trying to learn the coding nuances.
import java.io.*;
import java.util.*;
public class ImportTest {
public static void main(String[] args) throws IOException
{
Scanner s = null;
Scanner k = null;
ArrayList myList = new ArrayList<String>();
ArrayList myList2 = new ArrayList<String>();
ArrayList myList3 = new ArrayList<Student>();
try
{
s = new Scanner(new BufferedReader(new FileReader("testMe.txt")));
while (s.hasNext())
{
myList.add(s.nextLine());
}
}
finally
{
if (s != null)
{
s.close();
}
}
System.out.println("My List 1:");
for(int i=0; i<myList.size(); i++)
{
System.out.println(i+". "+myList.get(i));
}
for(int x=0; x<myList.size(); x++)
{
try
{
k = new Scanner(myList.get(x).toString());
while (k.hasNext())
{
myList2.add(k.next());
}
}
finally
{
if (k != null)
{
k.close();
}
}
String name;
int age;
double money;
name=myList2.get(0).toString();
age=Integer.parseInt(myList2.get(1).toString());
money=Double.parseDouble(myList2.get(2).toString());
Student myStudent=new Student(name, age, money);
myList3.add(myStudent);
myList2.clear();
}
System.out.println("Test of list object: ");
for(int i=0; i<myList3.size(); i++)
{
System.out.println(i+". "+myList3.get(i).toString());
}
}
}
I would read the file line by line and parse every line directly. This way you do not need 3 lists, 2 scanners and multiple iterations:
String line = "";
BufferedReader br = new BufferedReader(new FileReader("test.txt"));
ArrayList<Student> students = new ArrayList<Student>();
while( (line = br.readLine()) != null)
{
String[] tmp = line.split("\\s+"); //split line by spaces
//this needs bounds & error checking etc.
students.add(new Student(tmp[0], Integer.parseInt(tmp[1]), Double.parseDouble(tmp[2])));
}
In Java 7 you can use the new file functions to read all lines at once:
List<String> allLines = Files.readAllLines("test.txt", Charset.defaultCharset());
Do not forget to close the reader or use try-with-resources (since java 1.7)
Correct me if I am wrong, testMe.txt file contains Student information which are name, age, money, and you want read those values.
Best way to do it is you should serialize your Student objects into the the testMe.txt with the help of ObjectOutputStream. As well you can read those value using ObjectInputStream, so in this way you can able to get Student objects itself(no need to hnadle String).
In case you do want to serialize the data into file, you should store the data in some predefined format like as comma(,) or semi-colon(;) seperated.
For Example -
emp1, 24, 20000
emp emp2, 25, 24000
emp3, 26, 26000
In this case while reading the string you can split it with seperation character and get the actual information.
Code snippet:
List<Student> students = new ArrayList<Student>();
...
try(scanner = new Scanner(new BufferedReader(new FileReader("testMe.txt")))){
while (scanner.hasNext()){
String data[] = scanner.nextLine().split(",");
Student student = new Student(data[0],data[1],data[2]);
students.add(student);
}
}
Try-with-resource will automatically handle the resouce, you dont need to explicitly close it. This features available in java since 1.7.
I have the following text file (answers.txt):
Problem A: 23|47|32|20
Problem B: 40|50|30|45
Problem C: 5|8|11|14
Problem D: 20|23|25|30
What I need is something that will read the problem that I tell it(Problem A, Problem B), then read the numbers after it, which are separated by the lines, and print it out like this:
Answers for Problem A: a.23 b.47 c.32 d.20
Does anyone know how this can be done? I've been stuck on it for a while.
Read the lines one by one, split the lines at " " first. The you will get an array with three parts "Problem", "A:" and "23|47|32|20". Then split the third part at "|" so you will get a second array with four parts "23,"47","32","20".
Combine all to get the output you want.
If you want info on how to read lines from a file, or spilt strings then there are billions of tutorials online on how to do that so I wont go into detail on how its done. IM sure you can find them.
Check out this code!
It assumes that you have such file format:
Problem A:
23|7|32|20
Problem B:
40|50|30|45
Problem C:
5|8|11|14
Problem D:
20|23|25|30
because you wrote "numbers after it, which are separated by the lines"
import java.io.File;
import java.io.FileNotFoundException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Scanner;
public class Demo {
public static void main(String[] args) throws FileNotFoundException {
Scanner sc = new Scanner(new File("answers.txt"));
List<String> dataList = new ArrayList<String>();
while(sc.hasNextLine()){
dataList.add(sc.nextLine());
}
System.out.println(dataList);
Map<String,String> map = new HashMap<String,String>();
for(int i=0;i<dataList.size();i=i+2){
map.put(dataList.get(i),dataList.get(i+1));
}
for(Entry<String,String> en:map.entrySet()){
System.out.println(en.getKey()+" : "+en.getValue());
}
String problemC = map.get("Problem C:");
String splitted[] = problemC.split("\\|");
System.out.println("Get me problem C: "+String.format("a:%s, b:%s, c:%s, d:%s",splitted[0],splitted[1],splitted[2],splitted[3]));
}
}
Hope this helps!
public static void main(String args[])
{
BufferedReader br = new BufferedReader(new FileReader(new File("answers.txt")));
String lineRead = null;
String problem = "Problem A";//Get this from user Input
List<String> numberData = new ArrayList<String>();
while((lineRead = br.readLine())!=null)
{
if(lineRead.contains(problem))
{
StringTokenizer st = new StringTokenizer(lineRead,":");
String problemPart = st.nextToken();
String numbersPart = st.nextToken();
st = new StringTokenizer(lineRead,"|");
while(st.hasMoreTokens())
{
String number = st.nextToken();
System.out.println("Number is: " + number);
numberData.add(number);
}
break;
}
}
System.out.println("Answers for " + problem + " : " + numberData );
}
Read the lines one by one, split the lines with :. The you will get an array with two parts "Problem A:" and "23|47|32|20". Then split the second part at "|" so you will get a second array with four parts "23,"47","32","20".
Combining all this you will get the output you want.
Cheers!
Use java.util.Scanner and you can filter the integers in the file.
Scanner s = new Scanner (new File ("answers.txt")).useDelimiter("\\s+");
while (s.hasNext()) {
if (s.hasNextInt()) { // check if next token is integer
System.out.print(s.nextInt());
} else {
s.next(); // else read the next token
}
}
Do you know how to read line by line ? If not , chect it How to read a large text file line by line in java?
To sub your string data there have many ways to do. You can sub as you wish. Here for my code..
String data = yourReader.readLine();
String problem = data.substring("Problem".length(), data.indexOf(":"));
System.err.println("Problem is " + problem);
data = data.substring(data.indexOf(":") + 2, data.length());
String[] temp = data.split("\\|");
for (String result : temp) {
System.out.println(result);
}
Assuming there are always four possible answers as in your Example:
// read complete file in fileAsString
String regex = "^(Problem \\w+): (\\d+)\\|(\\d+)\\|(\\d+)\\|(\\d+)$";
Pattern pattern = Pattern.compile(regex);
Matcher matcher = pattern.matcher(fileAsString);
//and so on, read all the Problems using matcher.find() and matcher.group(int) to get the parts
// put in a Map maybe?
// output the one you want...
I might suggest creating a simple data type for the purpose of organization:
public class ProblemAnswer {
private final String problem;
private final String[] answers;
public ProblemAnswer(String problem, String[] answers) {
this.problem = problem;
this.answers = new String[answers.length];
for (int i = 0; i < answers.length; i++) {
this.answers[i] = answers[i];
}
}
public String getProblem() {
return this.problem;
}
public String[] getAnswers() {
return this.answers;
}
public String getA() {
return this.answers[0];
}
public String getB() {
return this.answers[1];
}
public String getC() {
return this.answers[2];
}
public String getD() {
return this.answers[3];
}
}
Then the reading from the text file would look something like this:
public void read() {
Scanner s = new Scanner("answers.txt");
ArrayList<String> lines = new ArrayList<String>();
while (s.hasNext()) {
lines.add(s.nextLine());//first separate by line
}
ProblemAnswer[] answerKey = new ProblemAnswer[lines.size()];
for (int i = 0; i < lines.size(); i++) {
String[] divide = lines.get(i).split(": "); //0 is the problem name, 1 is the list
//of answers
String[] answers = divide[1].split("|"); //an array of the answers to a given
//question
answerKey[i] = new ProblemAnswer(divide[0], answers); //add a new ProblemAnswer
//object to the key
}
}
Now that leaves you with an answer key with ProblemAnswer objects which is easily checked
with a simple .equals() comparison on the getProblem() method, and whatever index is matched, you have all the answers neatly arranged right within that same object.
I have a multidimensional array built from Strings that is initially created with the size [50][50], this is too big and now the array is full of null values, I am currently trying to remove these said null values, I have managed to resize the array to [requiredSize][50] but cannot shrink it any further, could anyone help me with this? I have scoured the internet for such an answer but cannot find it.
Here is my complete code too (I realise there may be some very unclean parts in my code, I am yet to clean anything up)
import java.io.*;
import java.util.*;
public class FooBar
{
public static String[][] loadCSV()
{
FileInputStream inStream;
InputStreamReader inFile;
BufferedReader br;
String line;
int lineNum, tokNum, ii, jj;
String [][] CSV, TempArray, TempArray2;
lineNum = tokNum = ii = jj = 0;
TempArray = new String[50][50];
try
{
BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
System.out.println("Please enter the file path of the CSV");
String fileName = in.readLine();
inStream = new FileInputStream(fileName);
inFile = new InputStreamReader(inStream);
br = new BufferedReader(inFile);
StringTokenizer tok,tok2;
lineNum = 0;
line = br.readLine();
tokNum = 0;
tok = new StringTokenizer(line, ",");
while( tok.hasMoreTokens())
{
TempArray[tokNum][0] = tok.nextToken();
tokNum++;
}
tokNum = 0;
lineNum++;
while( line != null)
{
line = br.readLine();
if (line != null)
{
tokNum = 0;
tok2 = new StringTokenizer(line, ",");
while(tok2.hasMoreTokens())
{
TempArray[tokNum][lineNum] = tok2.nextToken();
tokNum++;
}
}
lineNum++;
}
}
catch(IOException e)
{
System.out.println("Error file may not be accessible, check the path and try again");
}
CSV = new String[tokNum][50];
for (ii=0; ii<tokNum-1 ;ii++)
{
System.arraycopy(TempArray[ii],0,CSV[ii],0,TempArray[ii].length);
}
return CSV;
}
public static void main (String args[])
{
String [][] CSV;
CSV = loadCSV();
System.out.println(Arrays.deepToString(CSV));
}
}
The CSV file looks as follows
Height,Weight,Age,TER,Salary
163.9,46.8,37,72.6,53010.68
191.3,91.4,32,92.2,66068.51
166.5,51.1,27,77.6,42724.34
156.3,55.7,21,81.1,50531.91
It can take any size obviously but this is just a sample file.
I just need to resize the array so that it will not contain any null values.
I also understand a list would be a better option here but it is not possible due to outside constraints. It can only be an multi dimensional array.
I think you need 3 changes to your program
After your while loop lineNum will be 1 more than the number of lines in the file so instead of declaring CSV to String[tokNum][50] declare it as CSV = new String[tokNum][lineNum-1];
tokNum will be the number of fields in a row so your for loop condition should be ii<tokNum rather than ii<tokNum-1
The last parameter for your arraycopy should be lineNum-1
i.e. the modified code to build your CSV array is:
CSV = new String[tokNum][lineNum-1];
for (ii=0; ii<tokNum ;ii++)
{
System.arraycopy(TempArray[ii],0,CSV[ii],0,lineNum-1);
}
and the output will then be:
[[Height, 163.9, 191.3, 166.5, 156.3], [Weight, 46.8, 91.4, 51.1, 55.7],
[Age, 37, 32, 27, 21], [TER, 72.6, 92.2, 77.6, 81.1],
[Salary, 53010.68, 66068.51, 42724.34, 50531.91]]
Notice that you don't really need to handle the first line of the file separately from the others but that is something you can cover as part of your cleanup.
10 to 1 this is a homework assignment. However, it looks like you've put somethought into it.
Don't make the TempArray variable. Make a "List of List of Strings". Something like:
List<List<String>> rows = new ArrayList<ArrayList<String>>();
while(file.hasMoreRows()) { //not valid syntax...but you get the jist
String rowIText = file.nextRow(); //not valid syntax...but you get the jist
List<String> rowI = new ArrayList<String>();
//parse rowIText to build rowI --> this is your homework
rows.add(rowI);
}
//now build String[][] using fully constructed rows variable
Here's an observation and a suggestion.
Observation: Working with (multidimensional) arrays is difficult in Java.
Suggestion: Don't use arrays to represent complex data types in Java.
Create classes for your data. Create a List of people:
class Person {
String height; //should eventually be changed to a double probably
String weight; // "
//...
public Person( String height, String weight /*, ... */ ) {
this.height = height;
this.weight = weight;
//...
}
}
List<Person> people = new ArrayList<Person>();
String line;
while ( (line = reader.nextLine()) != null ) {
String[] records = line.split(",");
people.add(new Person (records[0], records[1] /*, ... */));
}