Re: Read file

rossum <>
Thu, 30 Jul 2009 10:03:13 +0100
On Thu, 30 Jul 2009 00:56:40 -0700 (PDT), Anabolik <>

I try to read the content of file text.txt. The size of this file is
26 Mb. And always I have the error:

Exception in thread "main" java.lang.OutOfMemoryError: Java heap space
    at java.util.Arrays.copyOf(
    at java.lang.AbstractStringBuilder.expandCapacity
    at java.lang.AbstractStringBuilder.append(
    at java.lang.StringBuffer.append(

at lines contents.append(text).append(System.getProperty

How can I read and save the content of file. The content of file I
need then in the program to show it in some dialog.

You file is too large to fit into your allocated heap. You can either
increase the heap until it is large enough to hold the entire file and
the rest of your program, or you can deal with the fine in chunks.
The size of a "chunk" is dependent on what you want to do with the

public static void main(String[] args) {
       File file = new File("D:\\work\\text.txt");
       StringBuffer contents = new StringBuffer();
       BufferedReader reader = null;

       try {
           reader = new BufferedReader(new FileReader(file));
           String text = null;

           // repeat until all lines is read
           while ((text = reader.readLine()) != null)

All you do with the file in this example is to print it to System.out,
so rather than accumilating the whole file before printing just print
what you have and throw it away:

  System.out.println(text + System.getProperty("line.separator"));

That way you have a maximum of one line in memory at one time. In
general read in the minimum amount of the file that you need to
process and when you have finished that part throw it away and read in
the next part. You are using a BufferedReader so there is no need to
do any additional file buffering - all of that is already done.

    read chunk from file
    process chunk
    save results
  until file finished


       } catch (FileNotFoundException e)
       } catch (IOException e)
       } finally
               if (reader != null)
           } catch (IOException e)

       // show file contents here

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