Basic HTML version of Foils prepared Sept 6 1998

Foil 36 Interfaces can be used as Classes in type specification

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 behave exactly as classes when used as a type.
2 The normal type declaration syntax "interfaceName variableName" declares a variable or parameter to be an instance of some class that implements interfaceName.
  • public class StudentBody {
  • Stream s;
  • Picture id_photo; // of interface storable
  • StudentRecord id_card; // of interface storable
  • . . .
  • public void register() {
  • save(id_photo);
  • save(id_card);
  • }
  • public void save(Storable o) {
  • o.store(s);
  • }
  • }
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