Demo.java

package sdet;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Optional;
import java.util.function.Predicate;
import java.util.stream.IntStream;
import java.util.stream.Stream;

public class Demo {

	public static void main(String[] args) {
		List<Integer> nums = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);

		List<Integer> even = new ArrayList<>();

//		for (Integer i : nums) {
//			if (isEven(i)) {
//				even.add(i);
//			}
//		}

		Predicate<Integer> isEven = (num) -> num % 2 == 0;

		for (Integer i : nums) {
			if (isEven.test(i)) {
				even.add(i);
			}
		}

		Stream<Integer> streamed = nums.stream();

		Stream<Integer> mapped = streamed.map(i -> i * i); // 1, 4, 9, 16, 36....

		Stream<Integer> greaterThan5 = mapped.filter(i -> i > 5); // 9, 16, 36 ...

		Stream<Integer> evens = greaterThan5.filter(isEven); // 16, 36 ...

//		Optional<Integer> result = evens.reduce((sum, next) -> {
//			return sum(sum, next);
//		});

		Optional<Integer> result = evens.reduce(Demo::sum);

		Integer _result = result.orElseThrow(RuntimeException::new);
//		System.out.println(result.orElse(-1));
//		evens.forEach(i -> System.out.println(i));

//		Stream<Integer> filtered = nums.stream().filter(isEven); // 2, 4, 6, 8, 10
//
//		System.out.println(even);
//
//		System.out.println(filtered.collect(Collectors.toList()));

		IntStream.range(1, 11).forEach(i -> System.out.println(i));
		IntStream.range(1, 11).forEach(System.out::println);
	}

	private static int sum(int a, int b) {
		return a + b;
	}

}