how to delete the content of text file without deleting itself

Question

I want to copy the content of file  A  to file  B   after the copying is done I want to clear the content of file  A  and want to write on it from its beginning  I can t delete file  A  as it is related to some other task   I was able to copy the content using java s file API readLine      but don t know how to clear the content of file and set the file pointer to the beginning of the file

User · Answer

FileOutputStream fos   openFileOutput    file name like -- gt  one txt     MODE PRIVATE   FileWriter fw   new FileWriter fos getFD     fw write

User · Answer

Simple  write nothing   FileOutputStream writer   new FileOutputStream  file txt    writer write      getBytes     writer close

User · Answer

I don t believe you even have to write an empty string to the file   PrintWriter pw   new PrintWriter  filepath txt    pw close

User · Answer

Just print an empty string into the file   PrintWriter writer   new PrintWriter file   writer print      writer close

User · Answer

One liner to make truncate operation   FileChannel open Paths get   home user file to truncate    StandardOpenOption WRITE  truncate 0  close      More information available at Java Documentation  https   docs oracle com javase 7 docs api java nio channels FileChannel html

User · Answer

You want the setLength   method in the class RandomAccessFile

User · Answer

Write an empty string to the file  flush  and close  Make sure that the file writer is not in append-mode  I think that should do the trick

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How about below   File temp   new File   lt your file name gt     if  temp exists          RandomAccessFile raf   new RandomAccessFile temp   rw        raf setLength 0

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After copying from A to B open file A again to write mode and then write empty string in it

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All you have to do is open file in truncate mode  Any Java file out class will automatically do that for you

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You can use  FileWriter fw   new FileWriter   your file path     PrintWriter pw   new PrintWriter fw   pw write      pw flush     pw close      Remember not to use  FileWriter fw   new FileWriter   your file path   true     True in the filewriter constructor will enable append

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If you don t need to use the writer afterwards the shortest and cleanest way to do it would be like that   new FileWriter   path to your file txt   close

User · Answer

using   New Java 7 NIO library  try           if  Files exists filePath getParent                   Files createDirectory filePath getParent                       if  Files exists filePath                 Files createFile filePath                        Empty the file content         writer   Files newBufferedWriter filePath           writer write              writer flush      The above code checks if Directoty exist if not creates the directory  checks if file exists is yes it writes empty string and flushes the buffer  in the end yo get the writer pointing to empty file

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One of the best companion for java is Apache Projects and please do refer to it  For file related operation you can refer to the Commons IO project   The Below one line code will help us to make the file empty   FileUtils write new File   your file path

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you can write a generic method as  its too late but below code will help you others   public static FileInputStream getFile File fileImport  throws IOException         FileInputStream fileStream   null      try           PrintWriter writer   new PrintWriter fileImport           writer print StringUtils EMPTY           fileStream   new FileInputStream fileImport             catch  Exception ex                ex printStackTrace              finally               writer close                       return fileStream

User · Answer

With try-with-resources writer will be automatically closed   import org apache commons lang3 StringUtils  final File file   new File  SomeFile    try  PrintWriter writer   new PrintWriter file          writer print StringUtils EMPTY                        here we can be sure that writer will be closed automatically

User · Answer

Just write   FileOutputStream writer   new FileOutputStream  file txt

[java] how to delete the content of text file without deleting itself

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