ahmad.mo74
جمعه 18 اردیبهشت 1394, 17:22 عصر
سلام. چیزی که پیشنهاد میکنم، استفاده از MappedByteBuffer هست. بخشی از documentation کلاس MappedByteBuffer :
/**
* A direct byte buffer whose content is a memory-mapped region of a file.
*
* <p> Mapped byte buffers are created via the {@link
* java.nio.channels.FileChannel#map FileChannel.map} method. This class
* extends the {@link ByteBuffer} class with operations that are specific to
* memory-mapped file regions.
*
* <p> A mapped byte buffer and the file mapping that it represents remain
* valid until the buffer itself is garbage-collected.
*
* <p> The content of a mapped byte buffer can change at any time, for example
* if the content of the corresponding region of the mapped file is changed by
* this program or another. Whether or not such changes occur, and when they
* occur, is operating-system dependent and therefore unspecified.
*
تا جایی که میدونم سریع ترین راه برای خوندن فایلهای بزرگ تو جاوا همین MappedByteBuffer هست.
import java.io.IOException;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.file.Paths;
/**
* @author avb
*/
public class LargeFileReadTest {
static final int FILE_CHUCK_SIZE = 1073741824; //1 GB
static final int BUFFER_SIZE = 1048576; //1 MB
public static void main(String[] args) throws IOException {
String fileName = "D:\\LargeFile.txt";
try (FileChannel inChannel = FileChannel.open(Paths.get(fileName))) {
long pos = 0, size = inChannel.size(), chunkSize;
while (size > 0) {
chunkSize = Math.min(FILE_CHUCK_SIZE, size);
MappedByteBuffer mappedByteBuffer = inChannel.map(FileChannel.MapMode.READ_ONLY, pos, chunkSize);
read(mappedByteBuffer);
mappedByteBuffer.clear();
size -= chunkSize;
pos += chunkSize;
}
}
}
static void read(MappedByteBuffer mappedByteBuffer) throws IOException {
byte[] bytes = new byte[BUFFER_SIZE];
while (mappedByteBuffer.hasRemaining()) {
int len = Math.min(bytes.length, mappedByteBuffer.remaining());
mappedByteBuffer.get(bytes, 0, len);
process(bytes);
}
}
static void process(byte[] bytes) throws IOException {
//process bytes
}
}
من خودم روی یه فایل متنی حدودا 3 گیگی تست کردم و بدون مشکل تونستم فایل رو بخونم.