Basic HTML version of Foils prepared Sept 6 1998

Foil 37 Further Features of Interfaces

From Java Tutorial 98-2: Java Language and Object Oriented Techniques CPS606 Fall Semester 1999 -- Sept 7 1999. by Geoffrey C. Fox, Nancy McCracken


1 Interfaces are either public or have the default friendly access (public for the package and private elsewhere)
2 Methods in an interface are always abstract and have the same access as the interface. No other modifiers may be applied
3 Variables in an interface are public, static, and final. They must be initialized.
4 Interfaces can incorporate one or more other interfaces, using the extends keyword:
  • public interface DoesItAll extends Storable, Paintable {
    • public abstract void doesSomethingElse();
    • }
5 A class can implement more than one interface:
  • public class Picture implements Storable, Paintable {
  • public void store(Stream s) {...}
  • public void retrieve(Stream s) {...}
  • public void refresh() {...}
  • }

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