Byte[] and java.lang.OutOfMemoryError reading file by bits

Question

I am trying to write a reader which reads files by bits but I have a problem with large files. I tried to read file with 100 mb and it took over 3 minutes but it worked.

Answer 1

I suggest you try memory mapping.

FileChannel fc = new FileInputStream(file).getChannel();
MappedByteBuffer mbb = fc.map(FileChannel.MapMode.READ_ONLY, 0, (int) fc.size());

This will make the whole file available almost immediately (about 10 ms) and uses next to no heap. BTW The file has to be less than 2 GB.