// with no parameter
() -> System.out.println("Hello, world.")

// with a single parameter (This example is an identity function).
a -> a

// with a single expression
(a, b) -> a + b

// with explicit type information
(long id, String name) -> "id: " + id + ", name:" + name

// with a code block
(a, b) -> { return a + b; }

// with multiple statements in the lambda body. It requires a code block.
// This example also includes two nested lambda expressions (the first one is also a closure).
(id, defaultPrice) -> {
  Optional<Product> product = productList.stream().filter(p -> p.getId() == id).findFirst();
  return product.map(p -> p.getPrice()).orElse(defaultPrice);
}