Fast stream reading in Java

To increase the performance of your Java application when reading from an InputStream, there are a few key areas to look into. If possible, don't make any reallocations of memory. Allocate the input buffer once. Let the Java VM do the bulk of the reading, i.e. read data in big chunks. Some coding examples show a loop that reads data a small amount at a time. This is sometimes inefficient. A much better technique is described below

If you know the maximum content length, the most optimal read would be a single line, like this:
len = instream.read( buf, 0, MAX_BUFFER_SIZE );

In this case we assume that the buffer has already been allocated with a size set to MAX_BUFFER_SIZE.

If the content is of varying size, we have to make a tradeoff between performance and memory usage. If you keep your buffer size just above the average content length, then the number of reallocations of the data buffer and the number of reads will be kept at a minimum. However if the average content length is too large to fit in memory, or if you only need access to sub sections at a time, it might be better to have the array size kept small and read from the stream.


Source http://developer.sonyericsson.com/site/global/techsupport/tipstrickscode/java/p_faststreamreadinginjava.jsp