Pseudo functional programming in Java

Main.java

public class Main {

  // Pseudo lambda
  public interface Operation {
    double apply(double arg);
  }

  // Takes in pseudo-lambda
  public static double times(Operation toApply, int times) {
    double result = 1.0;
    for (int i = 0; i < times; i++) {
      result = toApply.apply(result);
    }
    return result;
  }

  public static void main(String[] argv) {
    // Java refuses to let you use non-final variables inside an anonymous type.
    // so make it an array of size 1.
    final double[] fact = {10.0};
    
    // Pseudo-closure over `fact`
    Operation power = new Operation() {
      @Override
      public double apply(double arg) {
        return fact[0] * arg;
      }
    };

    // Use lambda `power` with method `times(...)`
    double result = times(power, 2);
    System.out.printf("Answer = %f\n", result);
  }
}