Convert file to byte array and vice versa

Question

I ve found many ways of converting a file to a byte array and writing byte array to a file on storage   What I want is to convert java io File to a byte array and then convert a byte array back to a java io File    I don t want to write it out to storage like the following     convert array of bytes into file FileOutputStream fileOuputStream   new FileOutputStream  C   testing2 txt     fileOuputStream write bFile   fileOuputStream close      I want to somehow do the following   File myFile   ConvertfromByteArray bytes

User · Answer

There is no such functionality but you can use a temporary file by File createTempFile     File temp   File createTempFile prefix  suffix      tell system to delete it when vm terminates  temp deleteOnExit

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Apache FileUtil gives very handy methods to do the conversion   try       File file   new File imagefilePath       byte   byteArray   new byte file length           byteArray   FileUtils readFileToByteArray file       catch Exception e        e printStackTrace

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You cannot do it for File  which is primarily an intelligent file path  Can you refactor your code so that it declares the variables  and passes around arguments  with type OutputStream instead of FileOutputStream  If so  see classes java io ByteArrayOutputStream and java io ByteArrayInputStream  OutputStream outStream   new ByteArrayOutputStream    outStream write whatever   outStream close    byte   data   outStream toByteArray    InputStream inStream   new ByteArrayInputStream data

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The file that you wanna convert into byte   File file new File   storage 0CE2-EA3D DCIM Camera VID 20190822 205931 mp4      FileInputStream fileInputStream new FileInputStream file   byte   data new byte  int  file length     BufferedInputStream bufferedInputStream new BufferedInputStream fileInputStream   bufferedInputStream read data 0 data length      Now the bytes of the file are contain in the  byte   data    If you want to convert these bytes into a file  you have to write these bytes to a  certain location  then it will make a new file at that location if same named file is  not available at that location   FileOutputStream fileOutputStream  new FileOutputStream Environment getExternalStoragePublicDirectory Environment DIRECTORY DOWNLOADS  toString     Video mp4    fileOutputStream write data       It will write or make a new file named Video mp4 in the  Download  directory of      the External Storage

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1- Traditional way  The traditional conversion way is through using read   method of InputStream as the following   public static byte   convertUsingTraditionalWay File file        byte   fileBytes   new byte  int  file length          try FileInputStream inputStream   new FileInputStream file                 inputStream read fileBytes             catch  Exception ex                 ex printStackTrace              return fileBytes      2- Java NIO  With Java 7  you can do the conversion using Files utility class of nio package   public static byte   convertUsingJavaNIO File file        byte   fileBytes   null      try               fileBytes   Files readAllBytes file toPath               catch  Exception ex                 ex printStackTrace              return fileBytes      3- Apache Commons IO  Besides JDK  you can do the conversion using Apache Commons IO library in 2 ways   3 1  IOUtils toByteArray    public static byte   convertUsingIOUtils File file        byte   fileBytes   null      try FileInputStream inputStream   new FileInputStream file                 fileBytes   IOUtils toByteArray inputStream             catch  Exception ex                 ex printStackTrace              return fileBytes      3 2  FileUtils readFileToByteArray    public static byte   convertUsingFileUtils File file        byte   fileBytes   null      try               fileBytes   FileUtils readFileToByteArray file             catch Exception ex                ex printStackTrace              return fileBytes

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Server side   RequestMapping   download   public byte   download   throws Exception       File f   new File  C   WorkSpace  Text  myDoc txt         byte   byteArray   new byte  int  f length             byteArray   FileUtils readFileToByteArray f           return byteArray      Client side  private ResponseEntity lt byte   gt  getDownload        URI end   URI create your url which server has exposed i e  bla                bla download       return rest getForEntity end byte   class       public static void main String   args  throws Exception         byte   byteArray   new TestClient   getDownload   getBody        FileOutputStream fos   new      FileOutputStream  C   WorkSpace  testClient  abc txt          fos write byteArray        fos close          System out println  file written successfully

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Otherwise Try this    Converting File To Bytes    import java io File    import java io FileInputStream    import java io FileNotFoundException    import java io IOException       public class Temp            public static void main String   args              File file   new File  c  EventItemBroker java              byte   b   new byte  int  file length              try                  FileInputStream fileInputStream   new FileInputStream file                  fileInputStream read b                  for  int i   0  i  lt  b length  i                                 System out print  char b i                                  catch  FileNotFoundException e                          System out println  File Not Found                           e printStackTrace                          catch  IOException e1                       System out println  Error Reading The File                         e1 printStackTrace                                  Converting Bytes to File        public class WriteByteArrayToFile             public static void main String   args                 String strFilePath    Your path               try                    FileOutputStream fos   new FileOutputStream strFilePath                    String strContent    Write File using Java                      fos write strContent getBytes                      fos close                           catch FileNotFoundException ex                       System out println  FileNotFoundException       ex                        catch IOException ioe                      System out println  IOException       ioe

User · Answer

I think you misunderstood what the java io File class really represents  It is just a representation of the file on your system  i e  its name  its path etc   Did you even look at the Javadoc for the java io File class  Have a look here If you check the fields it has or the methods or constructor arguments  you immediately get the hint that all it is  is a representation of the URL path   Oracle provides quite an extensive tutorial in their Java File I O tutorial  with the latest NIO 2 functionality too   With NIO 2 you can read it in one line using java nio file Files readAllBytes     Similarly you can use java nio file Files write   to write all bytes in your byte array   UPDATE  Since the question is tagged Android  the more conventional way is to wrap the FileInputStream in a BufferedInputStream and then wrap that in a ByteArrayInputStream  That will allow you to read the contents in a byte    Similarly the counterparts to them exist for the OutputStream

User · Answer

You can t do this  A File is just an abstract way to refer to a file in the file system  It doesn t contain any of the file contents itself   If you re trying to create an in-memory file that can be referred to using a File object  you aren t going to be able to do that  either  as explained in this thread  this thread  and many other places

[java] Convert file to byte array and vice versa

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