Split File - Java/Linux

Question

I have a large file contains nearly 250 million characters. Now, I want to split it into parts of each contains 30 million characters ( so first 8 parts will contains 30 million

Answer 1

You can try this. I have to used read/mode the first time as the file didn't exist at first. Youc an use read only as this code suggests.

long start = System.nanoTime();
long fileSize = 3200 * 1024 * 1024L;
FileChannel raf = new RandomAccessFile("deleteme.txt", "r").getChannel();
long midPoint = fileSize / 2 / 4096 * 4096;
MappedByteBuffer buffer1 = raf.map(FileChannel.MapMode.READ_ONLY, 0, midPoint + 4096);
MappedByteBuffer buffer2 = raf.map(FileChannel.MapMode.READ_ONLY, midPoint, fileSize - midPoint);
long time = System.nanoTime() - start;
System.out.printf("Took %.3f ms to map a file of %,d bytes long%n", time / 1e6, raf.size());

This is running on a Window 7 x64 box with 4 GB of memory.

Took 3.302 ms to map a file of 3,355,443,200 bytes long