out.writeInt( 0 );
out.writeDouble( 12.45 );

A good answer might be:

An int is 4 bytes (32 bits), a double is 8 bytes (64 bits) so the total is 12 bytes.

A DataOutputStream counts the number of bytes that have been written to the stream. The method size() returns this value as an int. The following program shows this:

import java.io.*;
class ByteCounter
{
  public static void main ( String[] args ) throws IOException
  {
    String fileName = "mixedTypes.dat" ;

    DataOutputStream dataOut = new DataOutputStream(
        new BufferedOutputStream(
        new FileOutputStream( fileName  ) ) );

    dataOut.writeInt( 0 );
    System.out.println( dataOut.size()  + " bytes have been written.");

    dataOut.writeDouble( 12.45 );
    System.out.println( dataOut.size()  + " bytes have been written.");

    dataOut.close();
  }
}

The output from this program is:

C:\Programs>java  ByteCounter
4 bytes have been written.
12 bytes have been written.

C:\Programs>

The method returns the total count of bytes written, not the number just written.

QUESTION 12:

Can several different data types be written to the same file?