java - What is the use of createing an Interface array assign to instantiated object -

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here have created object of b , assigned reference variable of interface.what means actually?. purpose of interface used implementation classes.what can interface when create array. means actually?. 

interface  i1{}  class implements i1{} class b implements i1{} class c extends b {} class d{}      public class lab1  {     public static void main(string[] args)     {          i1 i1[] = new b[4];         i1[0] = new a();         i1[1] = new c();         i1[2] = new b();         //i1[3] = new d();      }  }

it allows perform same operation on instances in array (by calling methods of interface).

for example :

for (i1 inst : i1) {     i1.dosomething (); // dosomething() method declared interface i1 }

to make less abstract, here's more concrete example - if interface called shape , has draw() method, can draw shapes writing :

for (shape shape : shapesarray) {     shape.draw (); }

this code doesn't care if actual instances stored in array circles, rectangles or polygons, long of them implement shape interface.


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