How to add a new line of text to an existing file in Java

Question

I would like to append a new line to an existing file without erasing the current information of that file  In short  here is the methodology that I am using the current time    import java io BufferedWriter  import java io FileWriter  import java io Writer   Writer output  output   new BufferedWriter new FileWriter my file name       clears file every time output append  New Line     output close      The problem with the above lines is simply they are erasing all the contents of my existing file then adding the new line text    I want to append some text at the end of the contents of a file without erasing or replacing anything

User · Answer

You can use the FileWriter String fileName  boolean append  constructor if you want to append data to file   Change your code to this   output   new BufferedWriter new FileWriter my file name  true      From FileWriter javadoc      Constructs a FileWriter object given a   file name  If the second argument is   true  then bytes will be written to   the end of the file rather than the   beginning

User · Answer

Try    r n   Java 7 example      append   true try PrintWriter output   new PrintWriter new FileWriter  log txt  true           output printf   s r n    NEWLINE       catch  Exception e

User · Answer

Starting from Java 7   Define a path and the String containing the line separator at the beginning   Path p   Paths get  C   Users  first last  test txt    String s   System lineSeparator      New Line      and then you can use one of the following approaches    Using Files write  small files    try       Files write p  s getBytes    StandardOpenOption APPEND     catch  IOException e        System err println e      Using Files newBufferedWriter text files    try  BufferedWriter writer   Files newBufferedWriter p  StandardOpenOption APPEND         writer write s     catch  IOException ioe        System err format  IOException   s n   ioe      Using Files newOutputStream  interoperable with java io APIs    try  OutputStream out   new BufferedOutputStream Files newOutputStream p  StandardOpenOption APPEND          out write s getBytes       catch  IOException e        System err println e      Using Files newByteChannel  random access files    try  SeekableByteChannel sbc   Files newByteChannel p  StandardOpenOption APPEND         sbc write ByteBuffer wrap s getBytes        catch  IOException e        System err println e      Using FileChannel open  random access files    try  FileChannel sbc   FileChannel open p  StandardOpenOption APPEND         sbc write ByteBuffer wrap s getBytes        catch  IOException e        System err println e        Details about these methods can be found in the Oracle s tutorial

User · Answer

you have to open the file in append mode  which can be achieved by using the FileWriter String fileName  boolean append  constructor   output   new BufferedWriter new FileWriter my file name  true      should do the trick

User · Answer

On line 2 change new FileWriter my file name  to new FileWriter my file name  true  so you re appending to the file rather than overwriting   File f   new File   path of the file            try               BufferedWriter bw   new BufferedWriter new FileWriter f  true                bw append line               bw close              catch  IOException e                System out println e getMessage

User · Answer

In case you are looking for a cut and paste method that creates and writes to a file  here s one I wrote that just takes a String input  Remove  true  from PrintWriter if you want to overwrite the file each time   private static final String newLine   System getProperty  line separator     private synchronized void writeToFile String msg         String fileName    c   TEMP  runOutput txt       PrintWriter printWriter   null      File file   new File fileName       try           if   file exists    file createNewFile            printWriter   new PrintWriter new FileOutputStream fileName  true            printWriter write newLine   msg         catch  IOException ioex            ioex printStackTrace          finally           if  printWriter    null                printWriter flush                printWriter close

User · Answer

The solution with FileWriter is working  however you have no possibility to specify output encoding then  in which case the default encoding for machine will be used  and this is usually not UTF-8   So at best use FileOutputStream       Writer writer   new BufferedWriter new OutputStreamWriter          new FileOutputStream file  true    UTF-8

[java] How to add a new line of text to an existing file in Java?

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