Merge pull request #87 from winterchord/polish_linked_list_exercise

Polish example linked-list exercise

linked-list/src/example/java/Deque.java

 public final class Deque<T> {
-    private Element head;
+    private Element<T> head;
 
     public void push(T value) {
         if (head == null) {
-            head = new Element(value, null, null);
-            head.setNext(head);
-            head.setPrev(head);
+            head = new Element<>(value, null, null);
+            head.next = head;
+            head.prev = head;
             return;
         }
 
-        Element oldTail = head.getPrev();
-        Element tail = new Element(value, oldTail, head);
-        oldTail.setNext(tail);
-        head.setPrev(tail);
+        Element<T> oldTail = head.prev;
+        Element<T> tail = new Element<>(value, oldTail, head);
+        oldTail.next = tail;
+        head.prev = tail;
     }
 
     public T pop() {
-        head = head.getPrev();
+        head = head.prev;
         return shift();
     }
 
     public void unshift(T value) {
         push(value);
-        head = head.getPrev();
+        head = head.prev;
     }
 
     public T shift() {
-        Object value = head.getValue();
+        T value = head.value;
 
-        Element newHead = head.getNext();
-        Element newTail = head.getPrev();
+        Element<T> newHead = head.next;
+        Element<T> newTail = head.prev;
 
         if (newHead == head) {
             head = null;
         }
         else {
-            newHead.setPrev(newTail);
-            newTail.setNext(newHead);
+            newHead.prev = newTail;
+            newTail.next = newHead;
             head = newHead;
         }
 
-        return (T) value;
+        return value;
+    }
+
+    private static final class Element<T> {
+        private final T value;
+        private Element<T> prev;
+        private Element<T> next;
+
+        public Element(T value, Element<T> prev, Element<T> next) {
+            this.value = value;
+            this.prev = prev;
+            this.next = next;
+        }
     }
 }

linked-list/src/example/java/Element.java

-public final class Element {
-    private final Object value;
-    private Element prev;
-    private Element next;
-
-    public Element(Object value, Element prev, Element next) {
-        this.value = value;
-        this.prev = prev;
-        this.next = next;
-    }
-
-    public Element getPrev() {
-        return prev;
-    }
-
-    public void setPrev(Element prev) {
-        this.prev = prev;
-    }
-
-    public Element getNext() {
-        return next;
-    }
-
-    public void setNext(Element next) {
-        this.next = next;
-    }
-
-    public Object getValue() {
-        return value;
-    }
-
-    @Override
-    public boolean equals(Object o) {
-        if (this == o) return true;
-        if (o == null || getClass() != o.getClass()) return false;
-
-        Element element = (Element) o;
-
-        if (value != null ? !value.equals(element.value) : element.value != null) return false;
-        if (prev != null ? !prev.equals(element.prev) : element.prev != null) return false;
-        return next != null ? next.equals(element.next) : element.next == null;
-
-    }
-
-    @Override
-    public int hashCode() {
-        int result = value != null ? value.hashCode() : 0;
-        result = 31 * result + (prev != null ? prev.hashCode() : 0);
-        result = 31 * result + (next != null ? next.hashCode() : 0);
-        return result;
-    }
-}

settings.gradle

 include 'hamming'
 include 'hexadecimal'
 include 'hello-world'
+include 'linked-list'
 include 'luhn'
 include 'meetup'
 include 'nth-prime'