Simple Interface Example

Interface Example
package mypackage;
public interface FirstInterface {
public int add (int a, int b);
}
 package mypackage;public class FirstClass implements FirstInterface {    public int add(int a, int b) {
        int c =0;
        c=a+b;
        return c;
    }}

package mypackage;public class SecondClass {
    SecondClass(){
   FirstClass a = new FirstClass();

  
    }
public void add(){
      FirstInterface a1=(FirstInterface)a;
      int d =a1.add(10, 20);
      System.out.println(""+d);
}
public static void main (String args[])
{
    SecondClass sc = new SecondClass();
    sc.add();
    System.out.println();
}
 FirstClass a = new FirstClass();
}