Re: Copy files in java gives me out of memory error

From:

Daniel Pitts <newsgroup.spamfilter@virtualinfinity.net>

Newsgroups:

comp.lang.java.help

Date:

Tue, 25 Dec 2007 09:33:01 -0800

Message-ID:

<1amdncol25FLo-zanZ2dnUVZ_gydnZ2d@comcast.com>

Canned wrote:

Hi,
I'm trying to create a class which only jobs is to copy any text files
before its get opened by text editor. I build a constructor that will
read from file then store its content in textContent variable. From
there, copy method would read from textContent and write its content in
a new file. But instead of doing its job, I get "Exception in thread
"main" java.lang.OutOfMemoryError: Java heap space
    at java.util.Arrays.copyOf(Arrays.java:2882)
    at
java.lang.AbstractStringBuilder.expandCapacity(AbstractStringBuilder.java:100)
    at java.lang.AbstractStringBuilder.append(AbstractStringBuilder.java:390)
    at java.lang.StringBuilder.append(StringBuilder.java:119)
    at v1.CreateBackup.<init>(CreateBackup.java:16)
    at v1.EditorSWT.openFileDialog(EditorSWT.java:150)
    at v1.EditorSWT.access$0(EditorSWT.java:141)
    at v1.EditorSWT$1.widgetSelected(EditorSWT.java:107)
    at org.eclipse.swt.widgets.TypedListener.handleEvent(Unknown Source)
    at org.eclipse.swt.widgets.EventTable.sendEvent(Unknown Source)
    at org.eclipse.swt.widgets.Widget.sendEvent(Unknown Source)
    at org.eclipse.swt.widgets.Display.runDeferredEvents(Unknown Source)
    at org.eclipse.swt.widgets.Display.readAndDispatch(Unknown Source)
    at v1.EditorSWT.main(EditorSWT.java:34)
"
Can someone please tell me what I'm doing wrong? I'm not very
experienced in Java

Quite simple, you're reading entire files into memory. More
specifically, you're reading the file into a StringBuilder. Don't do
that.

Use a FileInputStream, and a FileOutputStream, and copy a small amount
at a time (say 8k) using a byte array.
--
Daniel Pitts' Tech Blog: <http://virtualinfinity.net/wordpress/>