6.1-Writting Simple Lambdas

Question 1

📝️What is Functional programming?

Answer 1

It’s a way to write code in a declarative way.

• > So you specify what you want to do, rather than dealing with the state of objects.
• > You focus more on expressions than loops

Question 2

📝️How do we write in a Functional Programming style in Java?

Answer 2

By using Lambda Expressions …

aka Lambdas, Clousures

Question 3

📝️What is a Lambda Expression?

Answer 3

A lambda expression is a concise way to implement the Single Abstract Method of a Functional Interface

Question 4

📝️Why Lambdas? (4)

Answer 4

1. Enable Functional Programming (Declarative instead of Imperative)
2. Write a more comprehensible code
   - > This is more Readable and Concise)
3. Easier to use API’s & Libraries
4. Enables Parallel Programming

Question 5

📝️How to write Lambdas (Syntax)?

Answer 5

param-list -> statement(s);

param-list ::

• > 4 single-parameter (WITHOUT type) parentheses are optional.
• > parameter-type is optional when using parameter *** Type is infered by context (Functional Interfaces SAM)

-> Arror-operator

statement(s) ::

• > For single (return) statement curly braces are optional
• > If return keyword present or multiple statements curly braces are mandatory.

Question 6

📝️ What are the predifined Functional Interfaces? (4)

Answer 6

Predicate -> boolean test(T t)
Function -> R apply(T t)
Consumer -> void accept(T t)
Supplier -> T get()

Question 7

📝️ How to implement a Functional Interface?

Answer 7

• ** An interface can NOT be instantiated
  1. A concrete class that overrides the SAM method
  2. An Anonymous Class that overrides the SAM method
  3. A Lambda Expression
  4. Method Reference (A method with the same signature that is already implemented)

Question 8

When a Lambda Expression can be used?

Answer 8

When implementing the SAM of a Functional Interface

Question 9

How does a Lambda Expression infere the parameter types?

Answer 9

Because of the Context, a Lambda Expression implements a SAM from a Functional Interface