hussachai

package org.openjdk.jmh.samples;

import java.time.LocalDate;
import java.time.Month;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Random;

public class Pet {

hussachai

public class Pet {
    public static enum Type {
        CAT, DOG
    }
    public static enum Color {
        BLACK, WHITE, BROWN, GREEN
    }
    private String name;
    private Type type;
    private LocalDate birthdate;

hussachai

//Before Java 8
List<Pet> tmpList = new ArrayList<>();
for(Pet pet: pets){
    if(pet.getBirthdate().isBefore(LocalDate.of(2013, Month.JANUARY, 1))
            && pet.getWeight() > 50){
        tmpList.add(pet);
    }
}

hussachai

//Scala - strict collection
pets.filter { pet => pet.getBirthdate.isBefore(LocalDate.of(2013, Month.JANUARY, 1))}
	.filter { pet => pet.getWeight > 50 } //List[Pet]
//Scala - non-strict collection
pets.views.filter { pet => pet.getBirthdate.isBefore(LocalDate.of(2013, Month.JANUARY, 1))}
	.filter { pet => pet.getWeight > 50 } //SeqView[Pet]
//Scala - stream
pets.toStream.filter { pet => pet.getBirthdate.isBefore(LocalDate.of(2013, Month.JANUARY, 1))}
	.filter { pet => pet.getWeight > 50 } //Stream[Pet]

hussachai

//Java 8 - Stream
pets.stream()
    .filter(pet -> pet.getBirthdate().isBefore(LocalDate.of(2013, Month.JANUARY, 1)))
    .filter(pet -> pet.getWeight() > 50)
    .collect(toList())

hussachai

//Java 8 - Collection
pets.removeIf(pet -> !(pet.getBirthdate().isBefore(LocalDate.of(2013, Month.JANUARY, 1))
                    && pet.getWeight() > 50));
//Applying De-Morgan's law.
pets.removeIf(pet -> pets.get(0).getBirthdate().toEpochDay() >= LocalDate.of(2013, Month.JANUARY, 1).toEpochDay()
                || pet.getWeight() <= 50);

hussachai

def fibFrom(a: Int, b: Int): Stream[Int] = a #:: fibFrom(b, a + b)
val fib1 = fibFrom(0, 1) //0 1 1 2 3 5 8 …
val fib5 = fibFrom(0, 5) //0 5 5 10 15 …
//fib1.force //Don’t do this cause it will call the function infinitely and soon you will get the OutOfMemoryError
//fib1.size //Don’t do this too with the same reason as above.
fib1.take(10) //Do this. It will take the first 10 from the inifite Stream.
fib1.take(20).foreach(println(_)) //Prints 20 first numbers

hussachai

import java.util.ArrayList;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.NoSuchElementException;

/**
 * 
 * @author Hussachai
 *

hussachai

Filter Then Count
+----------+------------------------+-----------+---------+
| Language |       Benchmark        |   Score   |  Error  |
+----------+------------------------+-----------+---------+
| Java     | Collections            | 1,510,186 |  38,309 | <-- (3)
| Java     | Collections (removeIf) | 1,211,592 | 122,352 |
| Java     | Streams                | 5,145,467 |  83,952 | <-- (1)
| Scala    | Collections            | 3,603,865 |  66,801 | <-- (2)
| Scala    | Streams                |   234,396 |   2,542 |
| Scala    | Views                  | 1,079,969 |  23,248 |

hussachai

Sort then collect
+----------+-------------+---------+--------+
| Language |  Benchmark  |  Score  | Error  |
+----------+-------------+---------+--------+
| Java     | Collections | 173,910 |  2,738 | <-- (1)
| Java     | Streams     |  71,031 |    995 |
| Scala    | Collections |  92,693 |  1,079 | <-- (3)
| Scala    | Streams     |  53,167 |  1,220 |
| Scala    | Views       | 108,023 |  1,595 | <-- (2)
+----------+-------------+---------+--------+