Lambda, FunctionalInterface

lambda.md

FunctionalInterface (Java 8)

Functional Interface	Function Descriptor	Specific Interface
Predicate	T -> boolean	IntPredicate LongPredicate DoublePredicate
Consumer	T -> void	IntConsumer LongConsumer DoubleConsumer
Function	T -> R	IntFunction<R> IntToLongFunction IntToDoubleFunction LongFunction<R> LongToIntFunction LongToDoubleFunction DoubleFunction<R> DoubleToIntFunction DoubleToLongFunction ToIntFunction<T> ToLongFunction<T> ToDoubleFunction<T>
Supplier	() -> T	BooleanSupplier IntSupplier LongSupplier DoubleSupplier
UnaryOperator	T -> T	IntUnaryOperator LongUnaryOperator DoubleUnaryOperator
BinaryOperator	(T, T) -> T	IntBinaryOperator LongBinaryOperator DoubleBinaryOperator
BiPredicate	(T, U) -> boolean
BiConsumer	(T, U) -> void	ObjIntConsumer<T> ObjLongConsumer<T> ObjDoubleConsumer<T>
BiFunction	(T, U) -> R	ToIntBiFunction<T, U> ToLongBiFunction<T, U> ToDoubleBiFunction<T, U>

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Comparator - comparing, reversed, thenComparing

inventory.sort(Comparator.comparing(Apple:getWeight)
         .reversed()
         .thenComparing(Apple::getCountry));

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Predicate - and, or, negate

Predicate<Apple> notRedApple = redApple.negate();

Predicate<Apple> redAndHeavyAppleOrNotGreen = 
  redApple.and(apple -> apple.getWeight() > 150)
          .or(apple -> GREEN.equals(a.getColor()));            

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Function - andThen, compose

IntUnaryOperator f = i -> i + 1;
IntUnaryOperator g = i -> i * 3;

System.out.println("f(x) = x + 1");
System.out.println("g(x) = x * 3");
System.out.printf("g(f(2)) = %d\n", f.andThen(g).applyAsInt(2));  // 9
System.out.printf("f(g(2)) = %d\n",f.compose(g).applyAsInt(2));   // 7