Add comments for the classes.

Author: Kay Hudson

src/main/java/com/galvanize/LinkedList.java

@@ -1,3 +1,35 @@
+/*
+  Linked List
+
+  A linked list is a data structure that stores data sequentially by
+  linking each item in the list to the next. It has the following properties:
+
+  - head: the first item in the list
+  - tail (optional) : last item in the list
+
+  It's made up of items called Nodes, which contain 2 pieces of information:
+
+  - value: any type or you can restrict to specific types
+  - next: a reference to the next item in the list
+
+  Nodes are usually added to the end of the list. Operations include:
+
+  - Add node
+  - Remove node
+  - Find a node
+  For example, suppose you have a LinkedList of numbers. It might look
+  like so:
+
+  * [] represents the 'value' attribute
+  * -> represents the 'next' attribute
+  * Together, []-> represents a Node
+
+                    [100]-> [200]-> [300]-> null
+
+  The Node with value 100 is the head. The Node with value 300 is the
+  tail. Note how the tail points to nothing. Therefore null signifies
+  the end of the list.
+ */
 package com.galvanize;
 
 public class LinkedList {

src/main/java/com/galvanize/Node.java

@@ -1,3 +1,11 @@
+/*
+    Node
+
+    Nodes are the individual units contained in a data structure.
+
+    A node is a value object, representing any type of value and
+    providing a reference to the next node.
+ */
 package com.galvanize;
 
 import java.util.Objects;

src/main/java/com/galvanize/Stack.java

@@ -1,23 +1,24 @@
 package com.galvanize;
 
 public class Stack {
-    public boolean empty;
     public Node top;
     private int size;
 
     public Stack() {
-        this.empty = true;
         this.size = 0;
     }
 
     public int count() {
         return size;
     }
 
+    public boolean isEmpty() {
+        return this.count() == 0;
+    }
+
     public void push(Node item) {
         if (top == null) {
             top = item;
-            this.empty = false;
         } else {
             item.setNext(top);
             top = item;

src/test/java/StackTestCase.java

@@ -13,6 +13,11 @@ void setUp() {
         stack = new Stack();
     }
 
+    @Test
+    void testStackEmptyTrue() {
+        assertTrue(stack.isEmpty());
+    }
+
     @Test
     void testStackPushNode () {
         stack.push(new Node(100));
@@ -42,11 +47,6 @@ void testStackPeekReturnsTopNode() {
         assertEquals(topItem, peekItem);
     }
 
-    @Test
-    void testStackEmptyTrue() {
-        assertTrue(stack.empty);
-    }
-
     @Test
     void testNodesEqual() {
         Node treeNode = new Node("Tree");