Lamda & Stream API

java 8

Functional Progarmming

functional programming is a programming paradigm—a style of building the structure and elements of computer programs—that treats computation as the evaluation of mathematical functions and avoids changing-state and mutable data.

It is adeclarative programming paradigm, which means programming is done with expressions

Imperative + mutability

Declarative+

Immutability

Anonymous Inner Class

new Thread(
       new Runnable(){
            public void run(){
                System.out.println("I am another thread!");
               }
 
          }     
).start();

interface Runnable{
    public void run();
}

Functional Interface

interface Runnable{
    public void run();
}

Interface with exactly one method

interface Predicate<T> {
    boolean test(T t);
}

Predicate

using Anonymus class as function ...

void eligibleForDriving(){

     matchPerson(
            new Predicate<Person>(){
                public boolean test(Person p){
                 return p.getAge() >= 16;
                }
            }

        )
}

void eligibleForDriving(){

     matchPerson(
            new Predicate<Person>(){
                public boolean test(Person p){
                 return p.getAge() >= 16;
                }
            }

)
}

Lamda Expressions

{ who -> the hell is who }

void eligibleForDriving(){

     matchPerson(p -> p.age > 16);
}

 matchTwoPerson((p1,p2)-> p2.age-p1.age);

matchTwoPerson((p1,p2)->{
      int result;
      result = p2.age - p1.age;
      return result;
    });

Different Variants ....

What is Lamda ?

An anonymous Function
allows one to treat code as data
parameterize behaviour
provides closures
productive, flexible, "fluent" style programming

void eligibleForDriving(){

    matchPersons(p -> p.getAge() >= 16);
}

Lamda expressions are converted to instance of functional interface

Stream API

Thanks !!!

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