package Java8;

import java.util.Arrays;

import java.util.List;

public class Example4 {

public static void main(String[] args) {

List<Integer> values = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9);

// System.out.println(getUsingJava7(values));

System.out.println(getUsingJava8WithSepFunction(values));

}

// double the first even number in the list and it should be greater then 3

// o/p should be 4 * 2 = 8

private static Integer getUsingJava7(List<Integer> values) {

int result = 0;

for (Integer value : values) {

if (value > 3 && value % 2 == 0) {

result = value * 2;

break;

}

}

return result;

}

// lets do same thing using java8

// some times it throws null pointer exception

private static Integer getUsingJava8(List<Integer> values) {

// return values.stream().filter(e -> e > 3).filter(e -> e % 2 ==

// 0).map(e -> e * 2).findFirst();

return values.stream().filter(e -> e > 3).filter(e -> e % 2 == 0).map(e -> e * 2).findFirst().orElse(0);

}

// lets do some more generic way

// so create 3 different method 1 - greater than 3, 2 - %2 ==0 , 3 - *2

private static boolean isEven(int number) {

return number % 2 == 0;

}

private static boolean isGT3(int number) {

return number > 3;

}

private static int doubleIt(int number) {

return number*2;

}

private static Integer getUsingJava8WithSepFunction(List<Integer> values) {

return values.stream()

.filter(Example4::isGT3)

.filter(Example4::isEven)

.map(Example4::doubleIt)

.findFirst().orElse(0);

}

}