Is NIO really faster than java.io.*

[Sameer Amte]

Hi,
I have always used the java.io. classes for java IO. I tried to compare the performance of the io and nio classes FileChannel and ByteBuffers with the normal FileInput/OutputStreams and found that the normal java io was faster than nio.
I wrote a simple program that reads a file into a ByteBuffer/Byte Array and writes the output to a FileOutputStream/ByteBuffer.
The ByteBuffer requires additional operations that might be resulting in a delay. After every read you need to do a flip on a ByteBuffer and before every read(), you need to clear the buffer. These operations might be causing delays.
The code for the two approaches:

import java.io.*;
import java.nio.*;
import java.nio.channels.*;
 
public class NIOCopyFile
{
public static void main(String[] args)
{
try
{
FileInputStream fis = new FileInputStream("C:\\ngt\\pb\\adaptor\\scripts\\a.out");
FileOutputStream fos = new FileOutputStream("C:\\sameer1\\nio\\out.out");
FileChannel fcin = fis.getChannel();
FileChannel fcout = fos.getChannel();
//ByteBuffer buf = ByteBuffer.allocate((int)fcin.size());
ByteBuffer buf = ByteBuffer.allocate(1024);
int i =0;
long start=System.currentTimeMillis();
while(true)
{
int bytes=fcin.read(buf);
if (bytes ==-1)
{
break;
}
buf.flip();
fcout.write(buf);
buf.flip();
buf.clear();
}
long end=System.currentTimeMillis();
System.out.println("Execution Time = " + (end - start));
}
catch(IOException e)
{
System.out.println(e.getMessage());
e.printStackTrace();
}
}
}

import java.io.*;
 
public class OldIOCopyFile
{
public static void main(String[] args)
{
 
try
{
FileInputStream fis = new FileInputStream("C:\\ngt\\pb\\adaptor\\scripts\\a.out");
FileOutputStream fos = new FileOutputStream("C:\\sameer1\\nio\\oldout.out");
int i =0;
long start=System.currentTimeMillis();
while(true)
{
byte[] buf = new byte[1024];
int bytes=fis.read(buf);
if (bytes ==-1)
{
break;
}
fos.write(buf);
}
long end=System.currentTimeMillis();
System.out.println("Execution Time = " + (end - start));
}
catch(IOException e)
{
System.out.println(e.getMessage());
e.printStackTrace();
}
}
}

The Old IO class took less than 1 milisecond to complete and the new io class took 20 miliseconds to complete.

Any thoughts???

Thanks
Sameer

[Joe Ess]

The java.io.* classes are implemented using NIO (for example, FileInputStream has a getChannel() method) so the speed difference between the two should be negligable. The improvement NIO introduced was not speed, but new and interesting functionality that java.io.* did not have. See this article for some examples.