Recently gave a presentation in a Java Meetup in Bangalore on basics of functional programming, new functional features in Java 8, and introduction to the basic concepts of functional interfaces and lambda expressions...

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Introduction
to
Functional Programming
with Java-8
Dhruv Rai Puri
JavaBrahman.com

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HELLO!
I am Dhruv Rai Puri
I am a Java Architect and run the technical blog JavaBrahman.com
You can reach me at
dhruvraipuri@javabrahman.com
Twitter~ @javabrahman
facebook.com/JavaBrahman
plus.google.com/+JavaBrahman

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Whats going to be covered in this presentation
› Functional Programming
» What is functional programming
» How it’s different from imperative programming
› Important New Features in Java 8
› Functional Interfaces
› Lambda Expressions

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What is Functional Programming
Focusses on
WHAT
is to be done
Subset of Declarative Style of Programming

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Functional V/S Imperative
Programming
Style of Coding
Flow Control Mechanisms
Order of Execution Mutability of Variables
Primary Language Structures
Functions as 1st Class Objects
For in-depth understanding refer:
http://www.javabrahman.com/programming-principles/imperative-versus-functional-programming-paradigms-conceptual/

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New Functional Features in Java – 8
Lambda Expressions
Eg:(String param)->{System.out.println("My lambda says "+param);};
Functional Interfaces
Eg: @FunctionalInterface
public interface Predicate<T> {
boolean test(T t);
}
(cont…)

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New Functional Features in Java – 8(cont…)
Streams API
Eg: List filteredList = employeeList.stream()
.limit(2)
. collect(toList());
Method References
Eg: Function doubleConvertor=Double::parseDouble;
Constructor Reference: <ClassName>::new
For learning all new features in Java-8 refer:
http://www.javabrahman.com/java-8/new-features-in-java-8/

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Functional Interfaces
› interface which has only a single abstract method
3 Types of functional interfaces
public interface CustomFunctionalInterface {
public void firstMethod();
}
1› Custom or User Defined
(cont…)

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Functional Interfaces(cont..)
For learning in-depth about functional interfaces refer:
http://www.javabrahman.com/java-8/functional-interfaces-java-8/
//java.util.function.Predicate<T>
@FunctionalInterface
public interface Predicate<T> {
boolean test(T t);
}
2› Newly defined functional interfaces in Java 8
@FunctionalInterface
public interface Runnable {
public abstract void run();
}
3› Pre-existing functional interfaces in Java

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Lambda Expressions
For learning in-depth about lambda expressions refer:
http://www.javabrahman.com/java-8/lambda-expressions-java-8-explained-examples/
› anonymous function which can be passed around as a
parameter thus achieving Behavior Parameterization
@FunctionalInterface
public interface FirstInterface {
//the abstract method
public void singleMethod(String param);
}
(String param)->{System.out.println("My lambda says "+param);};
Functional Interface
Corresponding Lambda Expressions

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Q & A

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For further reading on Java-8
 http://www.javabrahman.com/java-8/new-features-in-java-8/
 http://www.javabrahman.com/java-8/functional-interfaces-java-8/
 http://www.javabrahman.com/java-8/lambda-expressions-java-8-explained-examples/
 http://www.javabrahman.com/java-8/java-8-method-references-tutorial-examples/
 http://www.javabrahman.com/java-8/constructor-references-java-8-simplified-tutorial/
 http://www.javabrahman.com/java-8/java-8-streams-api-tutorial-with-examples/

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Thank You