BufferedOutputStream

Here is the program again. Now it writes out 512 ints. A BufferedOutputStream is placed in the stream. This buffers the bytes before they are written to disk. Recall that a buffer is block of memory that is used to assemble data before it is written out all at once. (Somewhat like carrying your eggs in a basket rather than one by one.)

Buffering makes I/O operations more efficient. For a program that does massive I/O, buffering is essential. I/O is very slow compared to operations with main storage. Without buffering, I/O would be very, very slow. This program writes 512*4 == 2048 bytes, not really enough to worry about. But for practice, use a buffer.

import java.io.*;
class WriteInts
{
 public static void main ( String[] args )
 {
   String fileName = "intData.dat" ;

   try
   {      
     DataOutputStream out = new DataOutputStream(
         new BufferedOutputStream(
         new FileOutputStream( fileName )));

     for ( int j=0; j<512; j++ )
       out.writeInt( j );  

     out.close();
   }
   catch ( IOException iox )
   {
     System.out.println("Problem writing " + fileName );
   }
 }
}

QUESTION 8:

DataOutputStream has methods for writing out short, long, double and other data.

What do you suppose the method that writes a double is called?