RE: Understanding Implements

On 03/21/2001 at 09:04:24 AM, "Eyers, Daniel" <daniel.eyers@honeywell.com>
wrote:
I still a bit hazy on your statement "if you implement the required
methods."  Can you elaborate a bit....
--- end of excerpt ---
The ONLY way you can have a class that you can instantiate is
to implement ALL of the methods required by the interface.

If you DON'T implement all the required methods (the exact
ones in the interface, you have an abstract class).

I.e. if I have this interface and class in a file called Contract.java

public interface Contract {
  public void read();
  public void sign() throws NotReadException;
  public void payLegalFees() throws NotEnoughCashException;
}

class Mortgage implements Contract {
   public void lookAtProperty() {}
   public void compareProperty() {}

   public void read() throws NotReadException {}
   public void sign() {}
   // Skip this.
   // public void payLegalFees() throws NotEnoughCashException;
}

Contract.java:7: Mortgage should be declared abstract; it does not define
payLegalFees() in Mortgage
class Mortgage implements Contract {
^
1 error


"The stuff we call "software" is not like anything that human society
  is used to thinking about. Software is something like a machine, and
  something like mathematics, and something like language, and
  something like thought, and art, and information...
  but software is not in fact any of those other things."
Bruce Sterling - The Hacker Crackdown

Fred A. Kulack  -  AS/400e  Java and Java DB2 access, Jdbc, JTA, etc...
IBM in Rochester, MN  (Phone: 507.253.5982   T/L 553-5982)
mailto:kulack@us.ibm.com   Personal: mailto:kulack@bresnanlink.net
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