// No parameters
Runnable greet = () -> System.out.println("Hello!");

// One parameter, single expression (parentheses optional)
// takes a number, returns its square
java.util.function.Function<Integer, Integer> square = n -> n * n;

// Two parameters
java.util.function.BinaryOperator<Integer> add = (a, b) -> a + b;

// Multiple statements need braces and return
java.util.function.Function<Integer, String> describe = n -> {
  if (n > 0) return "positive";
  else return "not positive";
};