FunctionalChaining.java

import java.util.function.Function;
import java.util.stream.Stream;

public class FunctionalChaining {

  public static void main(String[] args) 
  {

	  Function<Double, Double> func1 = d -> d + 0.2;
	  Function<Double, Double> func2 = d -> d + 0.5;

	  // Simple chaining
	  System.out.println(func1.andThen(func2).apply(1.0));

	  // Chaining using Stream.of
	  Function<Double, Double> combined = Stream.of(func1, func2)
                                              .reduce(Function.identity(), Function::andThen);
	  System.out.println(combined.apply(1.0));

	  // Pass it to a function  which can accept variable number of functions.
	  System.out.println(combineFunctions(func1, func2));

	}

	private static Double combineFunctions(Function<Double, Double>... combineFunctions) 
	{
	  Function<Double, Double> chainedFunction = Stream.of(combineFunctions)
	                                                   .reduce(function -> function,Function::andThen);
	  return chainedFunction.apply(1.0);
	}

}