🚀 go-pugleaf

Hi, I try to start a method which uses readByte.
The code of the method goes here:

public static void kodiere(String sourcefile, String destinationfile) throws
IOException {

 DataInput sourcefile = new DataInputStream(new
FileInputStream(sourcefile));
 DataOutput destination = new DataOutputStream(new
FileOutputStream(destinationfile));
try {
 while(true){
 byte b = (byte) source.readByte(); // Read a byte from the source
 b = (byte) ((b+3)%256);
 destination.writeByte(b);}}

catch (EOFException e) // End of the source file.
{System.out.println("All right! Coding finished.");
}

when I have a statement like this:
kodiere(sourcefile,destinationfile);
... I get an Error message   "unreported Exception:java.io.IOException; must
be caught or declared to be thrown"

Now what is my mistake, what do I have to add??

Thanx for help
Marcel