Memory-mapping huge files in Java

Question

Is it possible to memory-map huge files (multiple GBs) in Java? This method of FileChannel looks promising: MappedByteBuffer map(FileChannel.MapMode mode, long position, long size) Both position and size allow for 64-bit values -- so far, so good. MappedByteBuffer, however, only provides methods for 32-bit positions (get(int index), position(int newPosition), etc.), which seems to imply that I cannot map files larger than 2 GB. How can I get around this limitation? JavaScript questions and answers, JavaScript questions pdf, JavaScript question bank, JavaScript questions and answers pdf, mcq on JavaScript pdf, JavaScript questions and solutions, JavaScript mcq Test , Interview JavaScript questions, JavaScript Questions for Interview, JavaScript MCQ (Multiple Choice Questions)

Answer 1

Take a look at Using a memory mapped file for a huge matrix code which shows how to create a list of MappedByteBuffer, each smaller then 2 GB, to map the entire file: private static final int MAPPING_SIZE = 1 << 30; ... long size = 8L * width * height; for (long offset = 0; offset < size; offset += MAPPING_SIZE) { long size2 = Math.min(size - offset, MAPPING_SIZE); mappings.add(raf.getChannel().map(FileChannel.MapMode.READ_WRITE, offset, size2)); } As per JDK-6347833 (fs) Enhance MappedByteBuffer to support sizes >2GB on 64 bit platforms the reason for the 2 GB limit is: A MappedByteBuffer is a ByteBuffer with additional operations to support memory-mapped file regions. To support mapping a region larger than Integer.MAX_VALUE would require a parallel hierarchy of classes. For now the only solution is create multiple MappedByteBuffers where each corresponds to a region that is no larger than 2GB.