An example to show how lambda expressions are mapped to the abstract mentods in functional interfaces

FunctionalInterFaceExample.java

class FunctionalInterFaceExample {

	/* Each lambda corresponds to a given type, specified by an interface.
	A so called functional interface must contain exactly one abstract method declaration. 
	Each lambda expression of that type will be matched to this abstract method. */

	@FunctionalInterface
	interface Converter<F, T> {
		T convert(F from);
	}

	public static void main(String[] args) {
		Converter<Double, Double> celciusToFarenheit = c -> (1.8*c + 32);
		Converter<Double, Double> farenheitToCelcius = f -> (f-32) / 1.8;

		Converter<Double, Double> celciusToKelvin = c -> c + 273.15;
		Converter<Double, Double> KelvinToCelcius = k -> k - 273.15;

		Converter<Double, Double> farenheitToKelvin = f -> (f + 459.67) + 5/9;
		Converter<Double, Double> kelvinToFarenheit = k -> k * 9/5 - 459.67;

		Converter<Integer, Double> intToDouble = i -> i + 0.00;

		System.out.println(farenheitToCelcius.convert(60.00));
	}
}