discussion on programming

$$Packages & Interfaces in java package my_package; import java.util.Scanner; interface perimeter1 { void calculate(); } class circle1 implements perimeter1 { private double r; public void calculate() { System.out.println("Enter radius:"); Scanner input=new Scanner(System.in); double r=input.nextDouble(); double p=2*3.14*r; System.out.println("perimeter of circle is:- "+p); } } class rectangle1 implements perimeter1 { private double length,breadth; public void calculate() { System.out.println("Eneter length"); Scanner input=new Scanner(System.in); double length=input.nextDouble(); System.out.println("Eneter breadth"); double breadth=input.nextDouble(); double p=2*(length+breadth); System.out.println("perimeter of rectangle is:- "+p); } } class main1 { public static void main(string args[]) { perimeter1 obj; circle1 obj1=new circle1(); rectangle1 ob...