Did you know:

• that LinkedList implements both Queue and List
• that this means you can remove and add items from the beginning and end of the list in constant  time
• that you should use  ArrayDeque instead of Stack
• that a Set does not allow duplicate entries
• that a HashSet uses hashCode() to store its entries
• that this is demonstrated by the set below printing out it’s content based on the number field of a Drink object

  package collections;
  
  import lombok.AllArgsConstructor;
  
  import java.util.Arrays;
  import java.util.HashSet;
  import java.util.Set;
  
  public class UseHashSet {
  
      public static void main(String[] args) {
          Drink firstDrink = new Drink("Cola", true, 13);
          Drink secondDrink = new Drink("Beer", true, 4);
          Drink thirdDrink = new Drink(   "Wiskey", false, 1);
          Drink fourthDrink = new Drink("Water", false, 14);
  
          Set<Drink> setOfDrinks = new HashSet<>(Arrays.asList(firstDrink, secondDrink, thirdDrink, fourthDrink));
  
          // [Drink{name='Wiskey', number=1}, Drink{name='Beer', number=4}, Drink{name='Cola', number=13}, Drink{name='Water', number=14}]
          System.out.println(setOfDrinks); 
      }
  
      @AllArgsConstructor
      static class Drink{
          private String name;
          private boolean isSparkley;
          private int number;
  
          @Override
          public String toString() {
              return "Drink{" +
                      "name='" + name + '\'' +
                      ", number=" + number +
                      '}';
          }
  
          @Override
          public int hashCode() {
              return number;
          }
      }
  }
  

• that Map is actually not a part of the Collection framework
• that offer() will add to the back of the queue and return true or false
• that add() will add to the back of the queue and return true or an exception
• that poll() will remove from the front of the queue and return the next element if there is any (else null)
• that remove() will remove from the front of the queue or throw an exception when queue is empty
• that pop() will remove from the front of the queue or throw an exception when queue is empty
• that peek() lets you spy on the front element of the queue without removing it
• that push()will add to the front of the queue and return void
• that you  cannot put null in ArrayDeque because it has methods that use null as a special return value
• that TreeMap and TreeSet are sorted
• and this means they call the compareTo() method
• that Map cannot contain duplicate keys
• but it can contain duplicate values
• that HashTable cannot contain null key nor values
• that Comparable  is often confused with Comparator
• that Comparable uses compareTo()
• and Comparator uses compare()
• that both are functional interface
• but only Comparator is commonly implemented with a lambda
• that it would be silly to implement Comparable with a lambda  since the point is to implement it in the object being compared
• that instead of using an anonymous class you can use a lambda expression
• if it call only one  method you can use a method reference
• that this is an example of a method reference:

• Consumer<String> consumer = s -> System.out.println(s);
  
  // can be written as
  
  Consumer<String> consumer = System.out::prinln;

• that Java8 introduced some nice methods to use on collections like removeIf(), replaceAll(), forEach()
• that Java8 also did the same for map eg. putIfAbsent() and merge()
• that this is an example of the merge() method and will print out Tom : Icecream, Nick : Fries and Loren : Strawberries on different lines:

• import java.util.HashMap;
  import java.util.Map;
  import java.util.function.BiFunction;
  
  public class UseMergeOnMap {
  
      public static void main(String[] args) {
  
          Map<String, String> favoriteFood = new HashMap<>();
          favoriteFood.put("Nick", "Fries");
          favoriteFood.put("Tom", null);
  
          BiFunction<String, String, String> mapper = (s1, s2) -> s1.compareTo(s2) < 0 ? s1 : s2;
  
          favoriteFood.merge("Nick", "Pancakes", mapper);
          favoriteFood.merge("Loren", "Strawberries", mapper);
          favoriteFood.merge("Tom", "Icecream", mapper);
  
          favoriteFood.forEach((k,v) -> System.out.println(k + " : " + v));
      }
  }

• that Vector implements List
• that Map uses put() instead of add()
• that you  just got a better understanding of  Java Collections
• that this is the end of the blogpost