How can I read comma separated values from a text file in Java

Question

I have got this text file with latitude and longitude values of different points on a map   How can I split my string into latitudes and longitudes  What is the general way to do these type of things that is with other delimiters like space or tab etc   Sample file   28 515046280572285 77 38258838653564 28 51430151808072 77 38336086273193 28 513566177802456 77 38413333892822 28 512830832397192 77 38490581512451 28 51208605426073 77 3856782913208 28 511341270865113 77 38645076751709   This is the code I am using to read from the file   try BufferedReader in   new BufferedReader new FileReader  C   test txt           String str      while   str   in readLine       null            System out println str           catch  IOException e        System out println  File Read Error

User · Answer

To split your String by comma    use str split      and for tab use str split    t        try           BufferedReader in   new BufferedReader                                 new FileReader  G   RoutePPAdvant2 txt             String str           while   str   in readLine      null                String   ar str split                                         in close          catch  IOException e            System out println  File Read Error

User · Answer

Use OpenCSV for reliability  Split should never be used for these kind of things  Here s a snippet from a program of my own  it s pretty straightforward  I check if a delimiter character was specified and use this one if it is  if not I use the default in OpenCSV  a comma   Then i read the header and fields  CSVReader reader   null  try       if  delimiter  gt  0            reader   new CSVReader new FileReader this csvFile   this delimiter             else           reader   new CSVReader new FileReader this csvFile                  these should be the header fields     header   reader readNext        while   fields   reader readNext       null               more code       catch  IOException e        System err println e getMessage

User · Answer

You may use the String split   method   String   tokens   str split         After that  use Double parseDouble   method to parse the string value to a double   double latitude   Double parseDouble tokens 0    double longitude   Double parseDouble tokens 1      Similar parse methods exist in the other wrapper classes as well - Integer  Boolean  etc

User · Answer

lat 3434 amp lon yy38 amp rd 1 0 amp   in that format o p is displaying  public class ReadText       public static void main String   args  throws Exception           FileInputStream f  new FileInputStream  D  workplace sample bookstore txt            BufferedReader br   new BufferedReader new InputStreamReader f            String strline          StringBuffer sb   new StringBuffer            while   strline   br readLine       null                        String   arraylist StringUtils split strline                    if arraylist length    2                   sb append  lat    append StringUtils trim arraylist 0    append   amp lon    append StringUtils trim arraylist 1    append   amp rt 1 0 amp                     else                   System out println  Error    strline                                   System out println  Data    sb toString

User · Answer

You can also use the java util Scanner class   private static void readFileWithScanner         File file   new File  path to your file file txt         Scanner scan   null       try           scan   new Scanner file            while  scan hasNextLine                  String line   scan nextLine                String   lineArray   line split                      do something with lineArray  such as instantiate an object       catch  FileNotFoundException e            e printStackTrace          finally           scan close

User · Answer

Use BigDecimal  not double  The Answer by adatapost is right about using String  split but wrong about using double to represent your longitude-latitude values  The float Float and double Double types use floating-point technology which trades away accuracy for speed of execution    Instead use BigDecimal to correctly represent your lat-long values   Use Apache Commons CSV library  Also  best to let a library such as Apache Commons CSV perform the chore of reading and writing CSV or Tab-delimited files    Example app  Here is a complete example app using that Commons CSV library  This app writes then reads a data file  It uses String  split for the writing  And the app uses BigDecimal objects to represent your lat-long values   package work basil example   import org apache commons csv CSVFormat  import org apache commons csv CSVPrinter  import org apache commons csv CSVRecord   import java io BufferedReader  import java io IOException  import java math BigDecimal  import java nio charset StandardCharsets  import java nio file Files  import java nio file Path  import java nio file Paths  import java time Instant  import java util List  import java util concurrent ThreadLocalRandom   public class LatLong         ----------   Write   -----------------------------     public void write   final Path path                 List  lt  String  gt  inputs                   List of                           28 515046280572285 77 38258838653564                             28 51430151808072 77 38336086273193                             28 513566177802456 77 38413333892822                             28 512830832397192 77 38490581512451                             28 51208605426073 77 3856782913208                             28 511341270865113 77 38645076751709                 Use try-with-resources syntax to auto-close the  CSVPrinter           try   final CSVPrinter printer   CSVFormat RFC4180 withHeader   latitude     longitude    print  path   StandardCharsets UTF 8                             for   String input   inputs                                 String   fields   input split                         printer printRecord  fields  0     fields  1                              catch   IOException e                         e printStackTrace                           ----------   Read   -----------------------------     public void read   Path path                    TODO  Add a check for valid file existing           try                          Read CSV file              BufferedReader reader   Files newBufferedReader  path                Iterable  lt  CSVRecord  gt  records   CSVFormat RFC4180 withFirstRecordAsHeader   parse  reader                for   CSVRecord record   records                                 BigDecimal latitude   new BigDecimal  record get   latitude                       BigDecimal longitude   new BigDecimal  record get   longitude                       System out println   lat      latitude       long      longitude                            catch   IOException e                         e printStackTrace                           ----------   Main   -----------------------------     public static void main   String   args                 LatLong app   new LatLong                Write         Path pathOutput   Paths get    Users basilbourque lat-long csv             app write  pathOutput            System out println   Writing file      pathOutput                Read         Path pathInput   Paths get    Users basilbourque lat-long csv             app read  pathInput             System out println   Done writing  amp  reading lat-long data file      Instant now

[java] How can I read comma separated values from a text file in Java?

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