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Message: <blockquote data-quote="sihina_lahiru" data-source="post: 7285054" data-attributes="member: 149577">4.Using an Interface as a Type             When you define a new interface, you are defining a new reference  data type. You can use interface names anywhere you can use any  other data type name. If you define a reference variable whose type  is an interface, any object you assign to it must be  an instance of a class that implements the interface.  As an example, here is a method for finding the largest object in a pair  of  objects, for any objects that are instantiated from a class that  implements Relatable: public Object findLargest(Object object1, Object object2) {    Relatable obj1 = (Relatable)object1;    Relatable obj2 = (Relatable)object2;    if ( (obj1).isLargerThan(obj2) > 0)       return object1;    else       return object2; } By casting object1 to a Relatable type, it can   invoke the isLargerThan method.  If you make a point of implementing Relatable in a wide  variety  of classes, the objects instantiated from any of those classes  can be compared with the  findLargest() method—provided that both objects are of the  same class.  Similarly, they can all be compared with the following methods: public Object findSmallest(Object object1, Object object2) {    Relatable obj1 = (Relatable)object1;    Relatable obj2 = (Relatable)object2;    if ( (obj1).isLargerThan(obj2) < 0)       return object1;    else       return object2; } public boolean isEqual(Object object1, Object object2) {    Relatable obj1 = (Relatable)object1;    Relatable obj2 = (Relatable)object2;    if ( (obj1).isLargerThan(obj2) == 0)       return true;    else       return false; } These methods work for any "relatable" objects, no matter what their  class inheritance is.  When they implement Relatable,  they can be of both their own class (or superclass) type and a Relatable  type. This gives them some of the advantages  of multiple inheritance, where they can have behavior from both a  superclass and an interface.         </blockquote>

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