Java使用ByteBuffer读取大文件

Posted 2020-08-15 swbzmx

import Java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;


public class ReadWriteCompare
{

public static void main(String[] args) throws IOException
{
FileInputStream fileInputStream = new FileInputStream("f:"+ File.separator +"IBM e-Mentor Program Kickoff Night 1105.pdf");
FileOutputStream fileOutputStream = new FileOutputStream("f:" + File.separator + "test.pdf");
   FileChannel inChannel = fileInputStream.getChannel();
FileChannel outChannel= fileOutputStream.getChannel();

ByteBuffer byteBuffer = ByteBuffer.allocate(1024);

   //Direct Buffer的效率会更高。
//   ByteBuffer byteBuffer = ByteBuffer.allocateDirect(1024);     

   long start = System.currentTimeMillis();
while(true)
{
int eof = inChannel.read(byteBuffer);
if(eof == -1 ) break;
byteBuffer.flip();
    outChannel.write(byteBuffer);
byteBuffer.clear();
}
System.out.println("spending : " + (System.currentTimeMillis()-start));
inChannel.close();
outChannel.close();
}

}