Buffer is to small

Question

In my web app I am using BufferedWriter so the user will be able to generate and download reports.

File evl = new File(tmpDirPath + "evl.xml");
portEVL.deleteOnExit();
fw = new FileWriter(evl);
bw = new BufferedWriter(fw);
bw.write(getHeader().concat(evlBuffer.toString()));

When writing to the buffer I get the following error message :

Caused By: 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)

I try to increase the buffer size but still the same error

Is there a why to separate the writing process or perhaps some other idea?

Answer 1

Your problem has nothing to do with the buffer space, you are running out of Heap space in your JVM!

Try increasing the heap size with these flags:

-Xms<size>        set initial Java heap size
-Xmx<size>        set maximum Java heap size
-Xss<size>        set java thread stack size

java -Xms16m -Xmx64m ClassName

The most important one for you is -Xmx<size> set maximum Java heap size

You can also always do it in gigabytes by putting java -Xmx2g ClassName

Here is the official Oracle documentation.