aruld

Latency Comparison Numbers
--------------------------
L1 cache reference                            0.5 ns
Branch mispredict                             5   ns
L2 cache reference                            7   ns             14x L1 cache
Mutex lock/unlock                            25   ns
Main memory reference                       100   ns             20x L2 cache, 200x L1 cache
Compress 1K bytes with Zippy              3,000   ns
Send 1K bytes over 1 Gbps network        10,000   ns    0.01 ms
Read 4K randomly from SSD*              150,000   ns    0.15 ms

aruld

import java.util.ArrayList;
import java.util.List;

public class LINQQueryExample {

    public static class Student {

        public String firstName;
        public String lastName;
        public int[] scores;

aruld

object TweetUtil {

  def main(args: Array[String]) {
    val keywords = List("brown", "fox", "dog", "pangram")
    val tweet = "The quick brown fox jumps over a lazy dog. #pangram http://www.rinkworks.com/words/pangrams.shtml"

    keywords.exists(tweet.contains)
    (keywords.foldLeft(false)( _ || tweet.contains(_) ))
  }
}

aruld

// take 1
keywords.stream().anyMatch(keyword -> tweet.contains(keyword));

// take 2 using method reference
keywords.stream().anyMatch(tweet::contains)

// take 3 using reduce()
keywords.stream().reduce(false, (Boolean b, String keyword) -> b || tweet.contains(keyword), (l, r) -> l | r);

aruld

package java.util.stream;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;

public class MyList<E> extends ArrayList<E> {

  public MyList(int initialCapacity) {
    super(initialCapacity);

aruld

package java.util.stream;

import java.util.function.Predicate;

public interface MyStream<T> extends Stream<T> {

  default boolean exists(Predicate<? super T> predicate) {
    return anyMatch(predicate);
  }
}

aruld

public class TweetUtil {

  public static void main(String[] args) {
    final List<String> keywords = Arrays.asList("brown", "fox", "dog", "pangram");
    final String tweet = "The quick brown fox jumps over a lazy dog. #pangram http://www.rinkworks.com/words/pangrams.shtml";

    exists(keywords, tweet);
  }

  public static boolean exists(List<String> keywords, String tweet) {

aruld

package java.util.stream;

import java.util.Spliterator;
import java.util.function.Predicate;
import java.util.function.Supplier;

public class MyReferencePipeline<T, U> extends ReferencePipeline<T, U> implements MyStream<U> {

  public MyReferencePipeline(Supplier<? extends Spliterator<?>> source, int sourceFlags, boolean parallel) {
    super(source, sourceFlags, parallel);

aruld

    List<String> google = Arrays.asList("android", "Android", "galaxy", "Galaxy", "nexus", "Nexus");

    List<String> apple = Arrays.asList("ios", "iOS", "iphone", "iPhone", "ipad", "iPad");

    List<Tweet> tweets = TweetReader.fromTweetSet(TweetReader.allTweets);

    // Using anyMatch and method reference
    List<Tweet> googleTweets = tweets.stream().filter(t -> (google.stream().anyMatch(t.text::contains))).collect(toList());
    
    List<Tweet> appleTweets = tweets.stream().filter(t -> (apple.stream().anyMatch(t.text::contains))).collect(toList());

aruld

    // Run with -Xbootclasspath/p:target/classes as ReferencePipeline access is now package local, so use this trick
    List<Tweet> googleTweets3 = tweets.stream().filter(tweet -> (new MyList<>(google).stream().exists(tweet.text::contains))).collect(toList());
    
    List<Tweet> appleTweets3 = tweets.stream().filter(tweet -> (new MyList<>(apple).stream().exists(tweet.text::contains))).collect(toList());