Java Lambda Expression Generic Functional Interfaces

// A generic functional interface. 
interface SomeFunc<T> {
  T func(T t);// ww  w  . j  a va  2  s .c  o m
}

public class Main {
  public static void main(String args[]) {
    // Use a String-based version of SomeFunc.
    SomeFunc<String> reverse = (str) -> {
      String result = "";
      int i;

      for (i = str.length() - 1; i >= 0; i--) {
        result += str.charAt(i);
      }
      return result;
    };

    System.out.println("Lambda reversed is " + reverse.func("Lambda"));
    System.out.println("Expression reversed is " + reverse.func("Expression"));

    // Now, use an Integer-based version of SomeFunc.
    SomeFunc<Integer> factorial = (n) -> {
      int result = 1;

      for (int i = 1; i <= n; i++)
        result = i * result;

      return result;
    };

    System.out.println("The factoral of 3 is " + factorial.func(3));
    System.out.println("The factoral of 5 is " + factorial.func(5));
  }
}