JDK8 Lambda expressions demo

1. Lambda Functions

2. Outline
 Behavior parameterization ?
 Lambda in nutshell
 Function Interface
 Type Checking
 Local variables and Closure
 Method reference

3. Behavior parameterization
 Demo

4. Lambda in nutshell
 Anonymous
 Passed around
 Concise

5. Syntax
 No Arguments
 One Argument
 Multiple Arguments
 With Explicit argument types
 Multiple Statements

6. Function Interface
 It’s an interface with exactly one abstract method.
 Example: Runnable, Callable, Comparator.
 A functional interface can have multiple default methods
 Functional descriptor

7. Common Functional Interfaces in JDK8

8. Type Checking
new OptSumOfNumbers().findSum(i -> true, numbers);
findSum(Predicate<Integer> predicate, List<Integer> numbers)
What is the functional descriptor for predicate ?
Functional descriptor Integer -> boolean matches lambda
expression.
Target Type:
Predicate<Integer>
Integer -> boolean

9. Restrictions on local variables & Closure
 Demo

10. Method reference
Lambda Method Reference Equivalent
(TripModel trip) -> trip.getTripId() TripModel::getTripId
(String s) -> System.out.println(s) System.out::println
(str, i) -> str.substring(i) String::substring
() -> Thread.currentThread().dumpStack() Thread.currentThread()::dumpStack

11. Method reference
 A method reference to a static method.
 A method reference to an instance method of an object of a particular type.
 A method reference to an instance method of an existing object.
 A method reference to a constructor.