EOFException - how to handle

Question

I m a beginner java programmer following the java tutorials   I am using a simple Java Program from the Java tutorials s Data Streams Page  and at runtime  it keeps on showing EOFException  I was wondering if this was normal  as the reader has to come to the end of the file eventually   import java io     public class DataStreams       static final String dataFile    F   Java  DataStreams  invoicedata txt        static final double   prices     19 99  9 99  15 99  3 99  4 99        static final int   units     12  8  13  29  50        static final String   descs              Java T-shirt            Java Mug            Duke Juggling Dolls            Java Pin            Java Key Chain             public static void main String args              try               DataOutputStream out   new DataOutputStream new BufferedOutputStream new FileOutputStream dataFile                  for  int i   0  i  lt  prices length  i                       out writeDouble prices i                    out writeInt units i                    out writeUTF descs i                               out close                catch IOException e               e printStackTrace       used to be System err println                       double price          int unit          String desc          double total   0 0           try               DataInputStream in   new DataInputStream new BufferedInputStream new FileInputStream dataFile                  while  true                    price   in readDouble                    unit   in readInt                    desc   in readUTF                    System out format  You ordered  d      units of  s at    2f n                   unit  desc  price                   total    unit   price                          catch IOException e                e printStackTrace                        System out format  Your total is  f  n    total             It compiles fine  but the output is   You ordered 12 units of Java T-shirt at  19 99 You ordered 8 units of Java Mug at  9 99 You ordered 13 units of Duke Juggling Dolls at  15 99 You ordered 29 units of Java Pin at  3 99 You ordered 50 units of Java Key Chain at  4 99 java io EOFException         at java io DataInputStream readFully Unknown Source          at java io DataInputStream readLong Unknown Source          at java io DataInputStream readDouble Unknown Source          at DataStreams main DataStreams java 39  Your total is 892 880000    From the Java tutorials s Data Streams Page  it says      Notice that DataStreams detects an end-of-file condition by catching EOFException  instead of testing for an invalid return value  All implementations of DataInput methods use EOFException instead of return values    So  does this mean that catching EOFException is normal  so just catching it and not handling it is fine  meaning that the end of file is reached   If it means I should handle it  please advise me on how to do it   EDIT  From the suggestions  I ve fixed it by using in available    gt  0 for the while loop condition   Or  I could do nothing to handle the exception  because it s fine

User · Answer

Alternatively  you could write out the number of elements first  as a header  using   out writeInt prices length     When you read the file  you first read the header  element count    int elementCount   in readInt     for  int i   0  i  lt  elementCount  i              read elements

User · Answer

Put your code inside the try catch block  i e     try    if in available    0          ------      catch EOFException eof         catch Exception e

User · Answer

You may come across code that reads from an InputStream and uses the snippet  while in available   gt 0  to check for the end of the stream  rather than checking for an  EOFException  end of the file    The problem with this technique  and the Javadoc does echo this  is that it only tells you the number of blocks that can be read without blocking the next caller  In other words  it can return 0 even if there are more bytes to be read  Therefore  the InputStream available   method should never be used to check for the end of the stream   You must use while  true  and  catch EOFException e      This isn t problem   catch  Other e      This is problem

User · Answer

You catch IOException which also catches EOFException  because it is inherited  If you look at the example from the tutorial they underlined that you should catch EOFException - and this is what they do  To solve you problem catch EOFException before IOException   try               catch EOFException e          eof - no error in this case   catch IOException e          something went wrong     e printStackTrace         Beside that I don t like data flow control using exceptions - it is not the intended use of exceptions and thus  in my opinion  really bad style

User · Answer

While reading from the file  your are not terminating your loop  So its read all the values and correctly throws EOFException on the next iteration of the read at line below   price   in readDouble     If you read the documentation  it says   Throws  EOFException - if this input stream reaches the end before reading eight bytes  IOException - the stream has been closed and the contained input stream does not support reading after close  or another I O error occurs   Put a proper termination condition in your while loop to resolve the issue e g  below       while in available    gt  0    lt --- if there are still bytes to read

User · Answer

The best way to handle this would be to terminate your infinite loop with a proper condition   But since you asked for the exception handling   Try to use two catches  Your EOFException is expected  so there seems to be no problem when it occures  Any other exception should be handled         catch  EOFException e              this is fine   catch IOException e           handle exception which is not expected     e printStackTrace

User · Answer

You can use while in available      0  instead of while true

[java] EOFException - how to handle?

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