From 3cbe62622a2c7e709e38f25d99f45b15c57b2445 Mon Sep 17 00:00:00 2001
From: jrtechs <jeffery@jrtechs.net>
Date: Sat, 25 Aug 2018 11:18:07 -0400
Subject: [PATCH] Created the stack data structure and made junit tests for it.

---
 .../DataStructures/Lists/Stack/IStack.java    | 18 +++++
 .../www/DataStructures/Lists/Stack/Stack.java | 80 +++++++++++++++++++
 .../net/jrtechs/www/DataStructures/Node.java  |  1 +
 .../www/DataStructures/Lists/StackTest.java   | 75 +++++++++++++++++
 4 files changed, 174 insertions(+)
 create mode 100644 src/main/java/net/jrtechs/www/DataStructures/Lists/Stack/IStack.java
 create mode 100644 src/main/java/net/jrtechs/www/DataStructures/Lists/Stack/Stack.java
 create mode 100644 src/test/java/net/jrtechs/www/DataStructures/Lists/StackTest.java

diff --git a/src/main/java/net/jrtechs/www/DataStructures/Lists/Stack/IStack.java b/src/main/java/net/jrtechs/www/DataStructures/Lists/Stack/IStack.java
new file mode 100644
index 0000000..6b08021
--- /dev/null
+++ b/src/main/java/net/jrtechs/www/DataStructures/Lists/Stack/IStack.java
@@ -0,0 +1,18 @@
+package net.jrtechs.www.DataStructures.Lists.Stack;
+
+/**
+ * Interface for defining behavior of a Stack
+ *
+ * @author Jeffery Russell 8-25-18
+ * @param <E>
+ */
+public interface IStack<E>
+{
+    public boolean empty();
+
+    public E peek();
+
+    public E pop();
+
+    public void push(E item);
+}
diff --git a/src/main/java/net/jrtechs/www/DataStructures/Lists/Stack/Stack.java b/src/main/java/net/jrtechs/www/DataStructures/Lists/Stack/Stack.java
new file mode 100644
index 0000000..f0b92c7
--- /dev/null
+++ b/src/main/java/net/jrtechs/www/DataStructures/Lists/Stack/Stack.java
@@ -0,0 +1,80 @@
+package net.jrtechs.www.DataStructures.Lists.Stack;
+
+import net.jrtechs.www.DataStructures.Node;
+
+/**
+ * @author Jeffery Russell 8-25-18
+ * @param <E> generic stored in collection
+ */
+public class Stack<E> implements IStack<E>
+{
+    /** Head node */
+    private Node<E> head;
+
+    public Stack()
+    {
+        this.head = null;
+    }
+
+    public Stack(E o)
+    {
+        this.head = new Node(o);
+    }
+
+
+    /**
+     * Determines if the stack is empty
+     *
+     * @return
+     */
+    @Override
+    public boolean empty()
+    {
+        return (this.head == null);
+    }
+
+
+    /**
+     * Retrieves top element with out removing it
+     *
+     * @return top element
+     */
+    @Override
+    public E peek()
+    {
+        if(this.head == null)
+            return null;
+        return head.getData();
+    }
+
+
+    /**
+     * Returns and removes top element from
+     * the stack.
+     *
+     * @return top element
+     */
+    @Override
+    public E pop()
+    {
+        if(this.empty())
+        {
+            return null;
+        }
+        E temp = this.head.getData();
+        this.head = this.head.getNext();
+        return temp;
+    }
+
+
+    /**
+     * Adds a new element to the Stack.
+     *
+     * @param item to add to stack
+     */
+    @Override
+    public void push(E item)
+    {
+        this.head = new Node<>(item, this.head);
+    }
+}
diff --git a/src/main/java/net/jrtechs/www/DataStructures/Node.java b/src/main/java/net/jrtechs/www/DataStructures/Node.java
index acb33e2..ab70838 100644
--- a/src/main/java/net/jrtechs/www/DataStructures/Node.java
+++ b/src/main/java/net/jrtechs/www/DataStructures/Node.java
@@ -6,6 +6,7 @@ package net.jrtechs.www.DataStructures;
 
 
 /**
+ * Class used for storing data in linked structures
  *
  * @param <E>
  */
diff --git a/src/test/java/net/jrtechs/www/DataStructures/Lists/StackTest.java b/src/test/java/net/jrtechs/www/DataStructures/Lists/StackTest.java
new file mode 100644
index 0000000..deed2d0
--- /dev/null
+++ b/src/test/java/net/jrtechs/www/DataStructures/Lists/StackTest.java
@@ -0,0 +1,75 @@
+package net.jrtechs.www.DataStructures.Lists;
+
+import net.jrtechs.www.DataStructures.Lists.Stack.Stack;
+import org.junit.Test;
+
+import static junit.framework.TestCase.assertFalse;
+import static junit.framework.TestCase.assertNotNull;
+import static junit.framework.TestCase.assertTrue;
+
+public class StackTest
+{
+
+    @Test
+    public void testCreation()
+    {
+        assertNotNull(new Stack<>(12.0));
+
+        assertNotNull(new Stack<>(14.0));
+    }
+
+    @Test
+    public void testInsertion()
+    {
+        Stack<Double> stack = new Stack<>();
+        stack.push(13.0);
+
+        stack.push(23.0);
+    }
+
+    @Test
+    public void testPeek()
+    {
+        Stack<Double> stack = new Stack<>();
+        stack.push(13.0);
+
+        stack.push(23.0);
+
+        assertTrue(stack.peek() == 23.0);
+    }
+
+
+    @Test
+    public void testPop()
+    {
+        Stack<Double> stack = new Stack<>();
+        stack.push(13.0);
+
+        stack.push(23.0);
+
+        assertTrue(stack.pop() == 23.0);
+        assertTrue(stack.pop() == 13.0);
+    }
+
+
+    @Test
+    public void testEmpty()
+    {
+        Stack<Double> stack = new Stack<>();
+
+        assertTrue(stack.empty());
+
+
+        Stack<Double> stack22 = new Stack<>(234.0);
+        assertFalse(stack22.empty());
+
+        stack.push(13.0);
+
+        stack.push(23.0);
+
+        assertTrue(stack.pop() == 23.0);
+        assertTrue(stack.pop() == 13.0);
+
+        assertTrue(stack.empty());
+    }
+}