package test.java;

import static org.junit.Assert.*;

import java.util.Arrays;

import java.util.List;

import org.junit.Test;

public class LambdaExpressionsTest {

@Test

public void sumOfOddNumbers_Usual() {

List<Integer> numbers = Arrays.asList(1, 3, 4, 6, 2, 7);

int sum = 0;

for (int number : numbers)

if (number % 2 != 0)

sum += number;

assertEquals(11, sum);

}

//No changes to state

@Test

public void sumOfOddNumbers_FunctionalProgrammingExample() {

List<Integer> numbers = Arrays.asList(1, 3, 4, 6, 2, 7);

int sum = numbers.stream() // Create Stream

.filter(number -> (number % 2 != 0)) // Intermediate Operation

.reduce(0, Integer::sum); // Terminal Operation

// number -> (number % 2 != 0) => Lambda Expression

// Integer::sum => Method Reference

// What is Functional Interface

assertEquals(11, sum);

}

@Test

public void lambdaExpression_predicate() {

List<Integer> numbers = Arrays.asList(1, 3, 4, 6, 2, 7);

numbers.stream()

.filter((number) -> (number % 2 != 0)) //Predicate

.forEach(number -> System.out.print(number)); //Consumer

// 137

}

static boolean isOdd(int number) {

return number % 2 != 0;

}

int i = 1_000_000;

//.map(String::toLowerCase)

//.map(s -> String.toLowerCase(s))

}