Java reading a file into an ArrayList

Question

How do you read the contents of a file into an ArrayList lt String gt  in Java    Here are the file contents   cat house dog         Just read each word into the ArrayList

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You can for example do this in this way  full code with exceptions handlig    BufferedReader in   null  List lt String gt  myList   new ArrayList lt String gt     try          in   new BufferedReader new FileReader  myfile txt         String str      while   str   in readLine       null            myList add str           catch  FileNotFoundException e        e printStackTrace      catch  IOException e        e printStackTrace      finally       if  in    null            in close

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CS124 HW6 Wikipedia Relation Extraction   Alan Joyce  ajoyce  public List lt String gt  addWives String fileName        List lt String gt  wives   new ArrayList lt String gt         try           BufferedReader input   new BufferedReader new FileReader fileName               for each line         for String line   input readLine    line    null  line   input readLine                  wives add line                     input close          catch IOException e            e printStackTrace            System exit 1           return null            return wives

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To share some analysis info  With a simple test how long it takes to read  1180 lines of values   If you need to read the data very fast  use the good old BufferedReader FileReader example  It took me  8ms  The Scanner is much slower  Took me  138ms  The nice Java 8 Files lines      is the slowest version   Took me  388ms

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A one-liner with commons-io   List lt String gt  lines   FileUtils readLines new File   path to file txt     utf-8      The same with guava   List lt String gt  lines         Files readLines new File   path to file txt    Charset forName  utf-8

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You can use   List lt String gt  list   Files readAllLines new File  input txt   toPath    Charset defaultCharset        Source  Java API 7 0

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Scanner scr   new Scanner new File filePathInString      Above line for scanning data from file        enter code here  ArrayList lt DataType gt  list   new ArrayList lt DateType gt       this is a object of arraylist which in data will store after scan    while  scr hasNext       list add scr next         above code is responsible for adding data in arraylist with the help of add function

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List lt String gt  words   new ArrayList lt String gt     BufferedReader reader   new BufferedReader new FileReader  words txt     String line  while   line   reader readLine       null        words add line     reader close

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Here s a solution that has worked pretty well for me   List lt String gt  lines   Arrays asList      new Scanner new File file   useDelimiter    Z   next   split    r   n        If you don t want empty lines  you can also do   List lt String gt  lines   Arrays asList      new Scanner new File file   useDelimiter    Z   next   split     r  n

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Simplest form I ever found is     List lt String gt  lines   Files readAllLines Paths get   path to file txt

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This Java code reads in each word and puts it into the ArrayList   Scanner s   new Scanner new File  filepath     ArrayList lt String gt  list   new ArrayList lt String gt     while  s hasNext         list add s next       s close      Use s hasNextLine   and s nextLine   if you want to read in line by line instead of word by word

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In Java 8 you could use streams and Files lines   List lt String gt  list   null  try  Stream lt String gt  lines   Files lines myPathToTheFile          list   lines collect Collectors toList       catch  IOException e        LOGGER error  Failed to load file    e       Or as a function including loading the file from the file system   private List lt String gt  loadFile         List lt String gt  list   null      URI uri   null       try           uri   ClassLoader getSystemResource  example txt   toURI          catch  URISyntaxException e            LOGGER error  Failed to load file    e              try  Stream lt String gt  lines   Files lines Paths get uri              list   lines collect Collectors toList           catch  IOException e            LOGGER error  Failed to load file    e             return list

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Add this code to sort the data in text file  Collections sort list

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Here is an entire program example   import java io File  import java io FileNotFoundException  import java util ArrayList  import java util Scanner   public class X       public static void main String   args        File f   new File  D  projects eric eclipseworkspace testing2 usernames txt            try              ArrayList lt String gt  lines   get arraylist from file f               for int x   0  x  lt  lines size    x                     System out println lines get x                                    catch Exception e               e printStackTrace                      System out println  done               public static ArrayList lt String gt  get arraylist from file File f           throws FileNotFoundException           Scanner s          ArrayList lt String gt  list   new ArrayList lt String gt             s   new Scanner f           while  s hasNext                  list add s next                       s close            return list

[java] Java reading a file into an ArrayList?

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