Lambda expressions Overview

Yousry IbrahimApril 27, 2016

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Agenda• What is the meaning of Lambda?• Functional interface.• Examples with built-in interfaces.• Traversing collections with lambda.• Example with new Interface.

What is the meaning of Lambda?

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–In the computer science lambda means function without a name.

–So it opens the door to functional programming.–Lambda let you define a Class with a single method or function with a special easy syntax.

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Functional interface

- In the quote for an early specs for lambda says

“Lambda expressions can only appear in places where they will be assigned to a variable whose type is a functional interface.”

http://cr.openjdk.java.net/~briangoetz/lambda/lambda-translation.html

- So Functional interfaces are These interfaces which have a single abstract method (before java 8 known as SAM Single Abstract Method )

- Some examples of Java built-in Functional interfaces :Runnable, Callable, Comparator, TimerTask

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Examples with built-in interfaces

Runnable Interface:- Before Java8 we used to make Thread as : - Or even by anonymous class without a name of the class

- we could use the inner classes as :

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Examples with built-in interfaces Con.

Runnable Interface:- Using Lambda Expressions with Java8 :

- As you can see the code significantly reduced and also become more readable by using lambda

– Now let me explain the syntax and what happened exactly in the previse example

- In case implementation more than one line

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Examples with built-in interfaces Con II.

Comparator Interface:- Before Java8 we used to use Comparator in such way:

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Examples with built-in interfaces Con III.

Comparator Interface:- Using Lambda expressions in Java8:

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Traversing collections with lambda.

- Before Lambda we could traverse collections as below:

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Traversing collections with lambda Con.

- Lets have a look on Array List Class:

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Traversing collections with lambda Con II.

- So we can write the previse code using Lambda as below

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Example with new Interface.

- We not only can used the built-in Interfaces But also can use new Interfaces with below steps:

1- Create your new Functional Interface using new annotation

2- Use your interface with Lambda Expressions:

The result is 50

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Thank youYousry