How to optimize this RW code? (full version)

Question

Hello: (Sorry for the wrong previous post, hope the moderator delete it)
I have this code:
import java.io.*;
class Number
    private byte val=0;
    public void Read(DataInputStream ar) throws Exception {val=ar.readByte();}
    public void Read(RandomAccessFile ar) throws Exception {val=ar.readByte();}
    public void Write(RandomAccessFile ar) throws Exception {ar.writeByte(val);}
    public void Write(DataOutputStream ar) throws Exception {ar.writeByte(val);}
}As you can see, I have methods for storing and writing into RandomAccessFiles and DataStreams. The code for RW is the same for both media. Is there any way to use the same code for Read(DataInputStream ar) and Read(RandomAccessFile ar)? Note that actually my class is more complex and can contain many data for RW: integers, doubles, objects, so that's why I want to simplify it. I thought about this possibility:
public void Read(Object ar)  throws Exception  
      if(ar instanceof RandomAccessFile) val= ((RandomAccessFile)ar).readByte();
      if(ar instanceof DataInputStream ) val= ((DataInputStream )ar).readByte();
public void Write(Object ar)  throws Exception  
      if(ar instanceof RandomAccessFile) val= ((RandomAccessFile)ar).writeByte(val);
      if(ar instanceof DataOutputStream ) val= ((DataOutputStream )ar).writeByte(val);
}But as you can see I have to make casts and repeat the code, I only got the advantage of having one single method.
Any suggestion?
Thanks!

Answer 1

Both DataOutputStream and RandomAccessFile implement the interfaces DataOutput, so you could do:
public void write(DataOutput out) throws Exception  
  out.writeByte(value);
}(the other case, RandomAccessFile and DataInputStream, use DataInput)