StreamsTest.java

package com.rajpro;

import java.io.File;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.Arrays;
import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;
import java.util.stream.Stream;

public class StreamsTest {
	private enum Status {
		OPEN, CLOSED
	};

	private static final class Task {
		private final Status status;
		private final Integer points;

		Task(final Status status, final Integer points) {
			this.status = status;
			this.points = points;
		}

		public Integer getPoints() {
			return points;
		}

		public Status getStatus() {
			return status;
		}

		@Override
		public String toString() {
			return String.format("[%s, %d]", status, points);
		}
	}

	public static void main(String[] args) throws Exception	{
		final Collection<Task> tasks = Arrays.asList(new Task(Status.OPEN, 5), new Task(Status.OPEN, 13),
				new Task(Status.CLOSED, 8));

		final long totalPointsOfOpenTasks = tasks.stream().filter(task -> task.getStatus() == Status.OPEN)
				.mapToInt(Task::getPoints).sum();
		System.out.println("Total points: " + totalPointsOfOpenTasks);
		System.out.println("************************************");
		System.out.println("Group tasks by status");
		final Map<Status, List<Task>> map = tasks.stream().collect(Collectors.groupingBy(Task::getStatus));
		System.out.println(map);
		System.out.println("**************************************");
		int totalPoints = 3;
		final Collection<String> result = tasks.stream() // Stream< String >
				.mapToInt(Task::getPoints) // IntStream
				.asLongStream() // LongStream
				.mapToDouble(points -> points / totalPoints) // DoubleStream
				.boxed() // Stream< Double >
				.mapToLong(weigth -> (long) (weigth * 100)) // LongStream
				.mapToObj(percentage -> percentage + "%") // Stream< String>
				.collect(Collectors.toList()); // List< String >
		System.out.println(result);
		System.out.println("**************************************************");
		final Path path = new File( "H:\\Preparation\\gitlearning.txt").toPath();
		try( Stream< String > lines = Files.lines( path, StandardCharsets.UTF_8 ) ) {
		lines.onClose( () -> System.out.println("Done!") ).forEach( System.out::println );
		}

	}
}