Started java collections

docs/java/basics/collections.md

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+# Collections
+
+Java has a class called `java.util.Collections` that defines all of the built in data types, but also provides some helper methods.
+
+## Helper Methods
+
+```java
+public static void main() {
+    Card[] cardArray = new Card[13];
+    Card aceOfHearts = Card.getFaceCard(Card.Suit.HEART, 'A');
+    Arrays.fill(cardArray, aceOfHearts);
+    Card.printDeck(Arrays.asList(cardArray), "Aces of Hearts", 1);
+
+    List<Card> cards = new ArrayList<>(52);
+    // doesn't add any cards because capacity is 52 but size is 0
+    Collections.fill(cards, aceOfHearts);
+    System.out.println(cards);
+    System.out.println("cards.size() = " + cards.size());
+
+    // Returns a list with n copies
+    List<Card> acesOfHearts = Collections.nCopies(13, aceOfHearts);
+    Card.printDeck(acesOfHearts, "Aces of Hearts", 1);
+
+    Card kingOfClubs = Card.getFaceCard(Card.Suit.CLUB, 'K');
+    List<Card> kingsOfClubs = Collections.nCopies(13, kingOfClubs);
+    Card.printDeck(kingsOfClubs, "Kings of Clubs", 1);
+
+    // adds elements to empty lists
+    Collections.addAll(cards, cardArray);
+    Collections.addAll(cards, cardArray);
+    Card.printDeck(cards, "Card Collection with Aces added", 2);
+
+    // copyies over elements at the same index
+    // in this example we have 26 cards already, so only the first 13 get overwritten
+    Collections.copy(cards, kingsOfClubs);
+    Card.printDeck(cards, "Card Collection with Kings copied", 2);
+
+    Collections.shuffle(cards);
+    Collections.reverse(cards);
+
+    var sortingAlgorithm = Comparator.comparing(Card::rank)
+        .thenComparing(Card::suit);
+    Collections.sort(cards, sortingAlgorithm);
+
+    List<Card> subList = new ArrayList<>(cards.subList(0,4));
+    int subListIndex = Collections.indexOfSubList(cards, subList);
+
+    // Returns true if no elements in second list are found in first list
+    boolean disjoint = Collections.disjoint(cards, subList);
+}
+```