How do I create a file and write to it

Question

What s the simplest way to create and write to a  text  file in Java

User · Answer

It s worth a try for Java 7     Files write Paths get    output txt     Information string herer  getBytes       It looks promising

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I think this is the shortest way   FileWriter fr   new FileWriter  your file name txt       After     write    your file extention    txt  in this case  fr write  Things you want to write into the file       Warning  this will REPLACE your old file content  fr close

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Note that each of the code samples below may throw IOException  Try catch finally blocks have been omitted for brevity  See this tutorial for information about exception handling   Note that each of the code samples below will overwrite the file if it already exists  Creating a text file   PrintWriter writer   new PrintWriter  the-file-name txt    UTF-8    writer println  The first line    writer println  The second line    writer close      Creating a binary file   byte data         FileOutputStream out   new FileOutputStream  the-file-name    out write data   out close      Java 7  users can use the Files class to write to files   Creating a text file   List lt String gt  lines   Arrays asList  The first line    The second line    Path file   Paths get  the-file-name txt    Files write file  lines  StandardCharsets UTF 8     Files write file  lines  StandardCharsets UTF 8  StandardOpenOption APPEND     Creating a binary file   byte data         Path file   Paths get  the-file-name    Files write file  data     Files write file  data  StandardOpenOption APPEND

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Since the author did not specify whether they require a solution for Java versions that have been EoL d  by both Sun and IBM  and these are technically the most widespread JVMs   and due to the fact that most people seem to have answered the author s question before it was specified that it is a text  non-binary  file  I have decided to provide my answer     First of all  Java 6 has generally reached end of life  and since the author did not specify he needs legacy compatibility  I guess it automatically means Java nbsp 7 or above  Java nbsp 7 is not yet EoL d by IBM   So  we can look right at the file I O tutorial  https   docs oracle com javase tutorial essential io legacy html     Prior to the Java SE 7 release  the java io File class was the   mechanism used for file I O  but it had several drawbacks          Many methods didn t throw exceptions when they failed  so it was   impossible to obtain a useful error message  For example  if a file   deletion failed  the program would receive a  delete fail  but   wouldn t know if it was because the file didn t exist  the user didn t   have permissions  or there was some other problem    The rename method   didn t work consistently across platforms    There was no real support   for symbolic links    More support for metadata was desired  such as   file permissions  file owner  and other security attributes  Accessing   file metadata was inefficient    Many of the File methods didn t scale    Requesting a large directory listing over a server could result in a   hang  Large directories could also cause memory resource problems    resulting in a denial of service    It was not possible to write   reliable code that could recursively walk a file tree and respond   appropriately if there were circular symbolic links       Oh well  that rules out java io File  If a file cannot be written appended  you may not be able to even know why     We can continue looking at the tutorial  https   docs oracle com javase tutorial essential io file html common  If you have all lines you will write  append  to the text file in advance  the recommended approach is https   docs oracle com javase 8 docs api java nio file Files html write-java nio file Path-java lang Iterable-java nio charset Charset-java nio file OpenOption   -  Here s an example  simplified    Path file        List lt String gt  linesInMemory        Files write file  linesInMemory  StandardCharsets UTF 8     Another example  append    Path file        List lt String gt  linesInMemory        Files write file  linesInMemory  Charset forName  desired charset    StandardOpenOption CREATE  StandardOpenOption APPEND  StandardOpenOption WRITE       If you want to write file content as you go  https   docs oracle com javase 8 docs api java nio file Files html newBufferedWriter-java nio file Path-java nio charset Charset-java nio file OpenOption   -  Simplified example  Java nbsp 8 or up    Path file        try  BufferedWriter writer   Files newBufferedWriter file         writer append  Zero header     append  0   write   r n                  Another example  append    Path file        try  BufferedWriter writer   Files newBufferedWriter file  Charset forName  desired charset    StandardOpenOption CREATE  StandardOpenOption APPEND  StandardOpenOption WRITE         writer write  ----------                  These methods require minimal effort on the author s part and should be preferred to all others when writing to  text  files

User · Answer

If we are using Java 7 and above and also know the content to be added  appended  to the file we can make use of newBufferedWriter method in NIO package   public static void main String   args        Path FILE PATH   Paths get  C  temp    temp txt        String text     n Welcome to Java 8          Writing to the file temp txt     try  BufferedWriter writer   Files newBufferedWriter FILE PATH  StandardCharsets UTF 8  StandardOpenOption APPEND             writer write text         catch  IOException e            e printStackTrace              There are few points to note    It is always a good habit to specify charset encoding and for that we have constant in class StandardCharsets  The code uses try-with-resource statement in which resources are automatically closed after the try    Though OP has not asked but just in case we want to search for lines having some specific keyword e g  confidential we can make use of stream APIs in Java     Reading from the file the first line which contains word  confidential  try       Stream lt String gt  lines   Files lines FILE PATH       Optional lt String gt  containsJava   lines filter l- gt l contains  confidential    findFirst        if containsJava isPresent             System out println containsJava get             catch  IOException e        e printStackTrace

User · Answer

The simplest way I can find   Path sampleOutputPath   Paths get   tmp testfile   try  BufferedWriter writer   Files newBufferedWriter sampleOutputPath         writer write  Hello  world         It will probably only work for 1 7

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Reading collection with customers and saving to file  with JFilechooser   private void writeFile         JFileChooser fileChooser   new JFileChooser this PATH       int retValue   fileChooser showDialog this   Save File         if  retValue    JFileChooser APPROVE OPTION            try  Writer fileWrite   new BufferedWriter new OutputStreamWriter new FileOutputStream fileChooser getSelectedFile                     this customers forEach  c  - gt                   try                      fileWrite append c toString    append   n                                      catch  IOException ex                       ex printStackTrace                                                        catch  IOException e               e printStackTrace

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public class Program       public static void main String   args            String text    Hello world           BufferedWriter output   null          try               File file   new File  example txt                output   new BufferedWriter new FileWriter file                output write text             catch   IOException e                 e printStackTrace              finally             if   output    null                 output close

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Just include this package   java nio file   And then you can use this code to write the file   Path file        byte   buf        Files write file  buf

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File reading and writing using input and outputstream     Coded By Anurag Goel   Reading And Writing Files import java io FileInputStream  import java io FileOutputStream  import java io IOException  import java io InputStream  import java io OutputStream    public class WriteAFile       public static void main String args              try               byte array        1   a   2   b   5                OutputStream os   new FileOutputStream  test txt                for int x 0  x  lt  array length   x                      os write  array x        Writes the bytes                           os close                 InputStream is   new FileInputStream  test txt                int size   is available                 for int i 0  i lt  size  i                      System out print  char is read                                     is close              catch IOException e                System out print  Exception

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One line only   path and line are Strings   import java nio file Files  import java nio file Paths   Files write Paths get path   lines getBytes

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public static void writefromFile ArrayList lt String gt  lines  String destPath            FileWriter fw          try               fw   new FileWriter destPath               for  String str   lines                    fw write str                             fw close               catch  IOException ex                JOptionPane showMessageDialog  ERROR  exception was      ex toString                       File f   new File destPath           f setExecutable true

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If you for some reason want to separate the act of creating and writing  the Java equivalent of touch is  try        create a file named  testfile txt  in the current working directory    File myFile   new File  testfile txt       if   myFile createNewFile             System out println  Success          else         System out println  Failure            catch   IOException ioe     ioe printStackTrace        createNewFile   does an existence check and file create atomically   This can be useful if you want to ensure you were the creator of the file before writing to it  for example

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Here s a little example program to create or overwrite a file  It s the long version so it can be understood more easily   import java io BufferedWriter  import java io File  import java io FileOutputStream  import java io IOException  import java io OutputStreamWriter  import java io Writer   public class writer       public void writing             try                 Whatever the file path is              File statText   new File  E  Java Reference bin images statsTest txt                FileOutputStream is   new FileOutputStream statText               OutputStreamWriter osw   new OutputStreamWriter is                   Writer w   new BufferedWriter osw               w write  POTATO                   w close              catch  IOException e                System err println  Problem writing to the file statsTest txt                         public static void main String  args            writer write   new writer            write writing

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In Java 8 use Files and Paths and using try-with-resources construct   import java io BufferedWriter  import java io IOException  import java nio file Files  import java nio file Paths   public class WriteFile      public static void main String   args  throws IOException           String file    text txt           System out println  Writing to file      file              Files newBufferedWriter   uses UTF-8 encoding by default         try  BufferedWriter writer   Files newBufferedWriter Paths get file                  writer write  Java n                writer write  Python n                writer write  Clojure n                writer write  Scala n                writer write  JavaScript n                 the file will be automatically closed

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If you already have the content you want to write to the file  and not generated on the fly   the java nio file Files addition in Java 7 as part of native I O provides the simplest and most efficient way to achieve your goals   Basically creating and writing to a file is one line only  moreover one simple method call   The following example creates and writes to 6 different files to showcase how it can be used   Charset utf8   StandardCharsets UTF 8  List lt String gt  lines   Arrays asList  1st line    2nd line    byte   data    1  2  3  4  5    try       Files write Paths get  file1 bin    data       Files write Paths get  file2 bin    data              StandardOpenOption CREATE  StandardOpenOption APPEND       Files write Paths get  file3 txt     content  getBytes         Files write Paths get  file4 txt     content  getBytes utf8        Files write Paths get  file5 txt    lines  utf8       Files write Paths get  file6 txt    lines  utf8              StandardOpenOption CREATE  StandardOpenOption APPEND     catch  IOException e        e printStackTrace

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To create file without overwriting existing file   System out println  Choose folder to create file    JFileChooser c   new JFileChooser    c setFileSelectionMode JFileChooser DIRECTORIES ONLY   c showOpenDialog c   c getSelectedFile    f   c getSelectedFile       File f - global variable String newfile   f      hi doc     txt or  doc or  html File file   new File newfile    try         System out println f       boolean flag   file createNewFile         if flag    true            JOptionPane showMessageDialog rootPane   File created successfully              else           JOptionPane showMessageDialog rootPane   File already exists                 Or use exists   function as follows          if file exists      true                JOptionPane showMessageDialog rootPane   File already exists                      else               JOptionPane showMessageDialog rootPane   File created successfully                       catch Exception e           Any exception handling method of your choice

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import java io File  import java io FileWriter  import java io IOException   public class FileWriterExample       public static void main String    args            FileWriter fw  null          File file  null          try               file new File  WriteFile txt                if  file exists                      file createNewFile                              fw   new FileWriter file               fw write  This is an string written to a file                fw flush                fw close                System out println  File written Succesfully              catch  IOException e                e printStackTrace

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best way is to use Java7  Java 7 introduces a new way of working with the filesystem  along with a new utility class     Files  Using the Files class  we can create  move  copy  delete files and directories as well  it also can be used to read and write to a file   public void saveDataInFile String data  throws IOException       Path path   Paths get fileName       byte   strToBytes   data getBytes         Files write path  strToBytes       Write with FileChannel If you are dealing with large files  FileChannel can be faster than standard IO  The following code write String to a file using FileChannel   public void saveDataInFile String data     throws IOException       RandomAccessFile stream   new RandomAccessFile fileName   rw        FileChannel channel   stream getChannel        byte   strBytes   data getBytes        ByteBuffer buffer   ByteBuffer allocate strBytes length       buffer put strBytes       buffer flip        channel write buffer       stream close        channel close        Write with DataOutputStream  public void saveDataInFile String data  throws IOException       FileOutputStream fos   new FileOutputStream fileName       DataOutputStream outStream   new DataOutputStream new BufferedOutputStream fos        outStream writeUTF data       outStream close        Write with FileOutputStream  Let   s now see how we can use FileOutputStream to write binary data to a file  The following code converts a String int bytes and writes the bytes to file using a FileOutputStream   public void saveDataInFile String data  throws IOException       FileOutputStream outputStream   new FileOutputStream fileName       byte   strToBytes   data getBytes        outputStream write strToBytes        outputStream close        Write with PrintWriter we can use a PrintWriter to write formatted text to a file   public void saveDataInFile   throws IOException       FileWriter fileWriter   new FileWriter fileName       PrintWriter printWriter   new PrintWriter fileWriter       printWriter print  Some String        printWriter printf  Product name is  s and its price is  d      iPhone   1000       printWriter close        Write with BufferedWriter  use BufferedWriter to write a String to a new file   public void saveDataInFile String data  throws IOException       BufferedWriter writer   new BufferedWriter new FileWriter fileName        writer write data        writer close        append a String to the existing file   public void saveDataInFile String data  throws IOException       BufferedWriter writer   new BufferedWriter new FileWriter fileName  true        writer append           writer append data        writer close

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package fileoperations  import java io File  import java io IOException   public class SimpleFile       public static void main String   args  throws IOException           File file  new File  text txt            file createNewFile            System out println  File is created            FileWriter writer   new FileWriter file               Writes the content to the file         writer write  Enter the text that you want to write             writer flush            writer close            System out println  Data is entered into file

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Here we are entering a string into a text file   String content    This is the content to write into a file   File file   new File  filename txt    FileWriter fw   new FileWriter file getAbsoluteFile     BufferedWriter bw   new BufferedWriter fw   bw write content   bw close       Be sure to close BufferedWriter   We can easily create a new file and add content into it

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If you wish to have a relatively pain-free experience you can also have a look at the Apache Commons IO package  more specifically the FileUtils class   Never forget to check third-party libraries  Joda-Time for date manipulation  Apache Commons Lang StringUtils for common string operations and such can make your code more readable    Java is a great language  but the standard library is sometimes a bit low-level  Powerful  but low-level nonetheless

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You can even create a temporary file using a system property  which will be independent of which OS you are using   File file   new File System  getProperty   java io tmpdir                          System  getProperty   file separator                           YourFileName txt

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There are at least several ways of creating a file and writing to it  Small files  1 7  You can use one of the write methods to write bytes  or lines  to a file  Path file   Paths get  quot path-to-file quot    byte   buf    quot text-to-write-to-file quot  getBytes    Files write file  buf    These methods take care of most of the work for you  such as opening and closing the stream  but are not intended for handling large files  Writing larger File by Using Buffered Stream I O  1 7  The java nio file package supports channel I O  which moves data in buffers  bypassing some of the layers that can bottleneck stream I O  String s    quot much-larger-text-to-write-to-file quot   try  BufferedWriter writer   Files newBufferedWriter file  StandardCharsets UTF 8         writer write s  0  s length        This approach is preferential due to its efficient performance especially when completing a large amount of write operations  Buffered operations have this effect as they aren   t required to call the operating system   s write method for every single byte  reducing on costly I O operations  Using NIO API to copy  and create a new one  a file with an Outputstream  1 7  Path oldFile   Paths get  quot existing-file-path quot    Path newFile   Paths get  quot new-file-path quot    try  OutputStream os   new FileOutputStream newFile toFile           Files copy oldFile  os      There are also additional methods that allow to copy all bytes from an input stream to a file  FileWriter  text    lt 1 7  Writes directly into file  less performance  and should be used only when number of writes are less  Used to write character-oriented data to a file  String s   quot some-text quot   FileWriter fileWriter   new FileWriter  quot C   path  to  file  file txt quot    fileWriter write fileContent   fileWriter close     FileOutputStream  binary    lt 1 7  FileOutputStream is meant for writing streams of raw bytes such as image data  byte data      quot binary-to-write-to-file quot  getBytes    FileOutputStream out   new FileOutputStream  quot file-name quot    out write data   out close     With this approach one should consider to always write an array of bytes rather than writing one byte at a time  The speedup can be quite significant - up to 10 x higher or more  Therefore it is recommended to use the write byte    methods whenever possible

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Use   try  Writer writer   new BufferedWriter new OutputStreamWriter new FileOutputStream  myFile txt    StandardCharsets UTF 8          writer write  text to write       catch  IOException ex           Handle me       Using try   will close stream automatically  This version is short  fast  buffered  and enables choosing encoding     This feature was introduced in Java 7

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Use   JFileChooser c   new JFileChooser    c showOpenDialog c   File writeFile   c getSelectedFile    String content    Input the data here to be written to your file    try       FileWriter fw   new FileWriter writeFile       BufferedWriter bw   new BufferedWriter fw       bw append content       bw append  hiiiii        bw close        fw close      catch  Exception exc       System out println exc

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Using Google s Guava library  we can create and write to a file very  easily   package com zetcode writetofileex   import com google common io Files  import java io File  import java io IOException   public class WriteToFileEx        public static void main String   args  throws IOException            String fileName    fruits txt           File file   new File fileName            String content    banana  orange  lemon  apple  plum            Files write content getBytes    file             The example creates a new fruits txt file in the project root directory

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In Java 7 and up   try  Writer writer   new BufferedWriter new OutputStreamWriter                new FileOutputStream  filename txt     utf-8          writer write  something        There are useful utilities for that though    FileUtils writeStringtoFile     from commons-io Files write     from guava   Note also that you can use a FileWriter  but it uses the default encoding  which is often a bad idea - it s best to specify the encoding explicitly   Below is the original  prior-to-Java 7 answer    Writer writer   null   try       writer   new BufferedWriter new OutputStreamWriter            new FileOutputStream  filename txt     utf-8         writer write  Something      catch  IOException ex           Report   finally      try  writer close     catch  Exception ex     ignore        See also  Reading  Writing  and Creating Files  includes NIO2

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A very simple way to create and write to a file in Java   import java io BufferedWriter  import java io File  import java io FileWriter   public class CreateFiles        public static void main String   args            try                 Create new file             String content    This is the content to write into create file               String path  D   a  hi txt               File file   new File path                   If file doesn t exists  then create it             if   file exists                      file createNewFile                               FileWriter fw   new FileWriter file getAbsoluteFile                 BufferedWriter bw   new BufferedWriter fw                   Write in file             bw write content                   Close connection             bw close                      catch Exception e               System out println e

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Creating a sample file   try       File file   new File   c  new-file txt        if file createNewFile              System out println  Successful created               else           System out println  Failed to create             catch  IOException e        e printStackTrace

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Here are some of the possible ways to create and write a file in Java    Using FileOutputStream  try     File fout   new File  myOutFile txt      FileOutputStream fos   new FileOutputStream fout     BufferedWriter bw   new BufferedWriter new OutputStreamWriter fos      bw write  Write somthing to the file          bw newLine      bw close      catch  FileNotFoundException e        File was not found   e printStackTrace      catch  IOException e         Problem when writing to the file   e printStackTrace        Using FileWriter  try     FileWriter fw   new FileWriter  myOutFile txt      fw write  Example of content      fw close      catch  FileNotFoundException e         File not found   e printStackTrace      catch  IOException e         Error when writing to the file   e printStackTrace        Using PrintWriter  try     PrintWriter pw   new PrintWriter  myOutFile txt      pw write  Example of content      pw close      catch  FileNotFoundException e         File not found   e printStackTrace      catch  IOException e         Error when writing to the file   e printStackTrace        Using OutputStreamWriter  try     File fout   new File  myOutFile txt      FileOutputStream fos   new FileOutputStream fout     OutputStreamWriter osw   new OutputStreamWriter fos     osw write  Soe content          osw close      catch  FileNotFoundException e         File not found   e printStackTrace      catch  IOException e         Error when writing to the file   e printStackTrace        For further check this tutorial about How to read and write files in Java

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This answer is centred on Java 8  and tries to cover all the details needed for the Java Professional Exam   It tries to explain why the different approaches exist  They each have their benefits  and each might be simplest in a given scenario  Classes involved include     -- OutputStream       -- FileOutputStream  -- Writer       -- OutputStreamWriter            -- FileWriter       -- BufferedWriter       -- PrintWriter  Java 5    -- Files  Java 7    FileOutputStream This class is meant for writing streams of raw bytes  All the Writer approaches below rely on this class  either explicitly or under the hood  try  FileOutputStream stream   new FileOutputStream  quot file txt quot           byte data      quot foo quot  getBytes        stream write data     catch  IOException e      Note that the try-with-resources statement takes care of stream close   and that closing the stream flushes it  like stream flush    all of the examples below use this approach   OutputStreamWriter This class is a bridge from character streams to byte streams  It can wrap a FileOutputStream  and write strings  Charset utf8   StandardCharsets UTF 8  try  OutputStreamWriter writer   new OutputStreamWriter new FileOutputStream new File  quot file txt quot     utf8         writer write  quot foo quot      catch  IOException e      BufferedWriter This class writes text to a character-output stream  buffering characters so as to provide for the efficient writing of single characters  arrays  and strings  It can wrap an OutputStreamWriter  try  BufferedWriter writer   new BufferedWriter new OutputStreamWriter new FileOutputStream new File  quot file txt quot             writer write  quot foo quot        writer newLine        method provided by BufferedWriter   catch  IOException e      Pre Java 5 this was the best approach for large files  with a regular try catch block   FileWriter This is a subclass of the OutputStreamWriter  and is a convenience class for writing character files  boolean append   false  try FileWriter writer   new FileWriter  quot file txt quot   append         writer write  quot foo quot        writer append  quot bar quot      catch  IOException e      The key benefit is that it has an optional append constructor argument  which determines whether it appends to or overwrites the existing file   Note that the append overwrite behaviour is not controlled by the write   and append   methods  which behave in nearly the same way  Note that   There is no buffering  but to handle large files it can be wrapped in a BufferedWriter  FileWriter uses the default encoding  It s often preferable to specify encoding explicitly  PrintWriter This class prints formatted representations of objects to a text-output stream  Under the hood it is the same as the BufferedWriter approach above  new BufferedWriter new OutputStreamWriter new FileOutputStream          PrintWriter was introduced in Java 5 as a convenient way to call this idiom  and adds additional methods such as printf   and println    Methods in this class don t throw I O exceptions  You can check errors by calling checkError    The destination of a PrintWriter instance can be a File  OutputStream or Writer   Here is an example of writing to a file  try  PrintWriter writer   new PrintWriter  quot file txt quot    quot UTF-8 quot          writer print  quot foo quot        writer printf  quot bar  d   quot    quot a quot   1       writer println  quot baz quot      catch  FileNotFoundException e      catch  UnsupportedEncodingException e      When writing to an OutputStream or Writer there is an optional autoFlush constructor parameter  which is false by default   Unlike the FileWriter  it will overwrite any existing file  Files write   Java 7 introduced java nio file Files  Files write   lets you create and write to a file in a single call   icza s answer shows how to use this method   A couple of examples  Charset utf8   StandardCharsets UTF 8  List lt String gt  lines   Arrays asList  quot foo quot    quot bar quot     try       Files write Paths get  quot file txt quot     quot foo quot  getBytes utf8        Files write Paths get  quot file2 txt quot    lines  utf8     catch  IOException e      This does not involve a buffer  so it s not suitable for large files  Files newBufferedWriter   Java 7 also introduced Files newBufferedWriter   which makes it easy to get a BufferedWriter  Charset utf8   StandardCharsets UTF 8  try  BufferedWriter writer   Files newBufferedWriter Paths get  quot file txt quot    utf8         writer write  quot foo quot      catch  IOException e      This is similar to PrintWriter  with the downside of not having PrintWriter s methods  and the benefit that it doesn t swallow exceptions  Summary  -----------------------------------------------------------------------------------                                         Buffer for           Can specify      Throws                                              large files            encoding      IOException      --------------------------- -------------------------- ------------- --------------      OutputStreamWriter           Wrap with BufferedWriter    Y              Y                  FileWriter                   Wrap with BufferedWriter                   Y                  PrintWriter                  Y                           Y                                 Files write                                              Y              Y                  Files newBufferedWriter      Y                           Y              Y                -----------------------------------------------------------------------------------

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There are some simple ways  like   File file   new File  filename txt    PrintWriter pw   new PrintWriter file    pw write  The world I m coming    pw close     String write    Hello World     FileWriter fw   new FileWriter file   BufferedWriter bw   new BufferedWriter fw    fw write write    fw close

[java] How do I create a file and write to it?

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