Java Practice Writing Java programs as required:

Write Java programs as required:

(1) write an interface:interfacea, which contains only one method, int (int n);

(2) write a class:ClassA to implement the interface interfacea, implement the int method ( int n) interface Side

the calculation of 1 to n is required;

(3) write another class:ClassB to Implement Interface Interfacea, Implementing int method (int n) Interface

method is required to calculate the factorial of n (n! );

(4) write test class e, test the implementation using the form of an interface callback in the main method oftest class e

The class of the interface.

 Package Pack1;  Public Interface interfacea {    int method (int  n);}

 package   Pack1;  public  class  ClassA implements   Interfacea {@Override  public  int  method (int   N) { ;  for  (int  I=0;i<=n;i++) {A  +=i;     return   A; }}

 package   Pack1;  public  class  ClassB implements   Interfacea {@Override  public  int  method (int   N) { ;  for  (int  I=1;i<=n;i++) {A  *=i;     return   A; }}

 Package Pack1;  Public class E {    publicstaticvoid  main (string[] args) {        interfacea A;        A=new  ClassA ();        System.out.println (A.method (5));        A=new  ClassB ();        System.out.println (A.method (5));}                    }

Java Practice Writing Java programs as required: