Oh-Oh to FunctionalIntroduction to Functional Thinking

naresh@agilefaqs.com@nashjain

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AgendaObject-Oriented Design Principles (SOLID, DRY)

Functional Concepts

Single Abstract Method (SAM) Pure Functions Immutability High-Order Functions Lambda Expressions Lazy evaluation Functional Composition Declarative vs. Imperative programming style

Quick Demo - Java 8 Functional Features

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Story #1

As a Kid learning arithmetics,

I want to identify even numbers

So that I can grow my understanding of odd and even numbers.

Acceptance Criteria#1

Given numbers 1, 2, 3, 4, 5 and 6

When using the Odd filter and emptying contents of the source bucket to target bucket

Then target bucket should contain 2, 4 and 6.

#2 Given numbers -2 and 3

When using the odd filter and emptying contents of the source bucket to target bucket

Then target bucket should contain -2.

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3 7

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Story #2

As a Kid learning arithmetics,

I want to identify prime numbers

So that I can differentiate between composite and prime numbers.

Acceptance Criteria#1

Given numbers 2, 4, 6, 7, 9 and 11

When using Prime filter and emptying contents of the source bucket to target bucket

Then target bucket should contain 2, 7 and 11.

#2 Given numbers -1, -2, 3, and 4

When using Prime filter and emptying contents of the source bucket to target bucket

Then target bucket should contain 3.

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Story #3

As a Kid learning arithmetics,

I want to identify odd primes

So that I can understand numbers that are odd and primes at the same time.

Acceptance CriteriaGiven numbers 2, 4, 5, 6 and 7

When using the Odd and prime filters and emptying contents of the source bucket to target bucket

Then target bucket should contain 5 and 7.

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xⁿ

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Story #4

As a Kid learning arithmetics,

I want to identify numbers within a range

So that I can grow my understanding of ranges.

Acceptance CriteriaGiven there are numbers 5, 7, 10 and 15

When using the range between 5..10 and emptying contents of the source bucket to target bucket

Then target bucket should contain 5, 7 and 10.

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5

3

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Story #5

As a Kid learning arithmetics,

I want to sum all the numbers that are in the bucket.

So that I can learn addition.

Acceptance Criteria

Given numbers 5, 7, 10 and 5

When using the aggregator and emptying contents of the source bucket to target bucket

Then target bucket should contain 27.

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6 4

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12

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Story #6

As a Kid learning arithmetics,

I want to multiply all numbers in a bucket.

So that I can grow my understanding of numbers.

Acceptance Criteria

Given numbers 2, 4 and 6

When using the multiplier and emptying contents of the source bucket to target bucket

Then target bucket should contain 48.

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6 4

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48

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Story #7

As a Kid learning arithmetics,

I want to sum all odd primes within a range.

So that I can grow my understanding of numbers.

Acceptance Criteria

Given numbers 1, 2, 5, 7, 8, 10 and 15

When using the range 2..10 and emptying contents of the source bucket to target bucket

Then target bucket should contain 12.

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4

5 1

2

6 4

∑

xⁿ

57

11

∑

12

Functional Features in Java 8

Quick Demo

Thank YouQuestions?

naresh@agilefaqs.com@nashjain