diff --git a/.idea/.name b/.idea/.name
new file mode 100644
index 0000000..b0f80fe
--- /dev/null
+++ b/.idea/.name
@@ -0,0 +1 @@
+Pricenton1
\ No newline at end of file
diff --git a/.idea/Princeton1.iml b/.idea/Princeton1.iml
new file mode 100644
index 0000000..d6ebd48
--- /dev/null
+++ b/.idea/Princeton1.iml
@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<module type="JAVA_MODULE" version="4">
+  <component name="NewModuleRootManager" inherit-compiler-output="true">
+    <exclude-output />
+    <content url="file://$MODULE_DIR$" />
+    <orderEntry type="inheritedJdk" />
+    <orderEntry type="sourceFolder" forTests="false" />
+  </component>
+</module>
\ No newline at end of file
diff --git a/.idea/gradle.xml b/.idea/gradle.xml
index 5ffbb1a..88c9aea 100644
--- a/.idea/gradle.xml
+++ b/.idea/gradle.xml
@@ -4,6 +4,8 @@
   <component name="GradleSettings">
     <option name="linkedExternalProjectsSettings">
       <GradleProjectSettings>
+        <option name="delegatedBuild" value="false" />
+        <option name="testRunner" value="PLATFORM" />
         <option name="externalProjectPath" value="$PROJECT_DIR$" />
         <option name="modules">
           <set>
@@ -14,6 +16,7 @@
             <option value="$PROJECT_DIR$/module5" />
             <option value="$PROJECT_DIR$/module6" />
             <option value="$PROJECT_DIR$/module7" />
+            <option value="$PROJECT_DIR$/module8" />
           </set>
         </option>
       </GradleProjectSettings>
diff --git a/.idea/modules.xml b/.idea/modules.xml
deleted file mode 100644
index 57e052a..0000000
--- a/.idea/modules.xml
+++ /dev/null
@@ -1,8 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<project version="4">
-  <component name="ProjectModuleManager">
-    <modules>
-      <module fileurl="file://$PROJECT_DIR$/.idea/modules/module4/Pricenton1.module4.test.iml" filepath="$PROJECT_DIR$/.idea/modules/module4/Pricenton1.module4.test.iml" />
-    </modules>
-  </component>
-</project>
\ No newline at end of file
diff --git a/module4/out/production/classes/com/hithomelabs/princeton1/module4/ArrayQueue$1.class b/module4/out/production/classes/com/hithomelabs/princeton1/module4/ArrayQueue$1.class
new file mode 100644
index 0000000..ff40074
Binary files /dev/null and b/module4/out/production/classes/com/hithomelabs/princeton1/module4/ArrayQueue$1.class differ
diff --git a/module4/out/production/classes/com/hithomelabs/princeton1/module4/ArrayQueue.class b/module4/out/production/classes/com/hithomelabs/princeton1/module4/ArrayQueue.class
new file mode 100644
index 0000000..b746ea7
Binary files /dev/null and b/module4/out/production/classes/com/hithomelabs/princeton1/module4/ArrayQueue.class differ
diff --git a/module4/out/production/classes/com/hithomelabs/princeton1/module4/ArrayStack$1.class b/module4/out/production/classes/com/hithomelabs/princeton1/module4/ArrayStack$1.class
new file mode 100644
index 0000000..b601e8c
Binary files /dev/null and b/module4/out/production/classes/com/hithomelabs/princeton1/module4/ArrayStack$1.class differ
diff --git a/module4/out/production/classes/com/hithomelabs/princeton1/module4/ArrayStack.class b/module4/out/production/classes/com/hithomelabs/princeton1/module4/ArrayStack.class
new file mode 100644
index 0000000..3aeb433
Binary files /dev/null and b/module4/out/production/classes/com/hithomelabs/princeton1/module4/ArrayStack.class differ
diff --git a/module4/out/production/classes/com/hithomelabs/princeton1/module4/Deque$1.class b/module4/out/production/classes/com/hithomelabs/princeton1/module4/Deque$1.class
new file mode 100644
index 0000000..af9ed30
Binary files /dev/null and b/module4/out/production/classes/com/hithomelabs/princeton1/module4/Deque$1.class differ
diff --git a/module4/out/production/classes/com/hithomelabs/princeton1/module4/Deque$Node.class b/module4/out/production/classes/com/hithomelabs/princeton1/module4/Deque$Node.class
new file mode 100644
index 0000000..929bdf4
Binary files /dev/null and b/module4/out/production/classes/com/hithomelabs/princeton1/module4/Deque$Node.class differ
diff --git a/module4/out/production/classes/com/hithomelabs/princeton1/module4/Deque.class b/module4/out/production/classes/com/hithomelabs/princeton1/module4/Deque.class
new file mode 100644
index 0000000..98be39e
Binary files /dev/null and b/module4/out/production/classes/com/hithomelabs/princeton1/module4/Deque.class differ
diff --git a/module4/out/production/classes/com/hithomelabs/princeton1/module4/LinkedQueue$1.class b/module4/out/production/classes/com/hithomelabs/princeton1/module4/LinkedQueue$1.class
new file mode 100644
index 0000000..7fdea7c
Binary files /dev/null and b/module4/out/production/classes/com/hithomelabs/princeton1/module4/LinkedQueue$1.class differ
diff --git a/module4/out/production/classes/com/hithomelabs/princeton1/module4/LinkedQueue$Node.class b/module4/out/production/classes/com/hithomelabs/princeton1/module4/LinkedQueue$Node.class
new file mode 100644
index 0000000..7badf05
Binary files /dev/null and b/module4/out/production/classes/com/hithomelabs/princeton1/module4/LinkedQueue$Node.class differ
diff --git a/module4/out/production/classes/com/hithomelabs/princeton1/module4/LinkedQueue.class b/module4/out/production/classes/com/hithomelabs/princeton1/module4/LinkedQueue.class
new file mode 100644
index 0000000..530a8a5
Binary files /dev/null and b/module4/out/production/classes/com/hithomelabs/princeton1/module4/LinkedQueue.class differ
diff --git a/module4/out/production/classes/com/hithomelabs/princeton1/module4/LinkedStack$1.class b/module4/out/production/classes/com/hithomelabs/princeton1/module4/LinkedStack$1.class
new file mode 100644
index 0000000..f77f5ae
Binary files /dev/null and b/module4/out/production/classes/com/hithomelabs/princeton1/module4/LinkedStack$1.class differ
diff --git a/module4/out/production/classes/com/hithomelabs/princeton1/module4/LinkedStack$Node.class b/module4/out/production/classes/com/hithomelabs/princeton1/module4/LinkedStack$Node.class
new file mode 100644
index 0000000..3480f02
Binary files /dev/null and b/module4/out/production/classes/com/hithomelabs/princeton1/module4/LinkedStack$Node.class differ
diff --git a/module4/out/production/classes/com/hithomelabs/princeton1/module4/LinkedStack.class b/module4/out/production/classes/com/hithomelabs/princeton1/module4/LinkedStack.class
new file mode 100644
index 0000000..a86fe16
Binary files /dev/null and b/module4/out/production/classes/com/hithomelabs/princeton1/module4/LinkedStack.class differ
diff --git a/module4/out/production/classes/com/hithomelabs/princeton1/module4/Queue.class b/module4/out/production/classes/com/hithomelabs/princeton1/module4/Queue.class
new file mode 100644
index 0000000..5af4244
Binary files /dev/null and b/module4/out/production/classes/com/hithomelabs/princeton1/module4/Queue.class differ
diff --git a/module4/out/production/classes/com/hithomelabs/princeton1/module4/Stack.class b/module4/out/production/classes/com/hithomelabs/princeton1/module4/Stack.class
new file mode 100644
index 0000000..923753c
Binary files /dev/null and b/module4/out/production/classes/com/hithomelabs/princeton1/module4/Stack.class differ
diff --git a/module4/out/test/classes/com/hithomelabs/princeton1/module4/ArrayQueueTest.class b/module4/out/test/classes/com/hithomelabs/princeton1/module4/ArrayQueueTest.class
new file mode 100644
index 0000000..ec761de
Binary files /dev/null and b/module4/out/test/classes/com/hithomelabs/princeton1/module4/ArrayQueueTest.class differ
diff --git a/module4/out/test/classes/com/hithomelabs/princeton1/module4/ArrayStackTest.class b/module4/out/test/classes/com/hithomelabs/princeton1/module4/ArrayStackTest.class
new file mode 100644
index 0000000..c10fdc2
Binary files /dev/null and b/module4/out/test/classes/com/hithomelabs/princeton1/module4/ArrayStackTest.class differ
diff --git a/module4/out/test/classes/com/hithomelabs/princeton1/module4/LinkedQueueTest.class b/module4/out/test/classes/com/hithomelabs/princeton1/module4/LinkedQueueTest.class
new file mode 100644
index 0000000..83c3a78
Binary files /dev/null and b/module4/out/test/classes/com/hithomelabs/princeton1/module4/LinkedQueueTest.class differ
diff --git a/module4/src/main/java/com/hithomelabs/princeton1/module4/ArrayQueue.java b/module4/src/main/java/com/hithomelabs/princeton1/module4/ArrayQueue.java
index 8576647..34aea75 100644
--- a/module4/src/main/java/com/hithomelabs/princeton1/module4/ArrayQueue.java
+++ b/module4/src/main/java/com/hithomelabs/princeton1/module4/ArrayQueue.java
@@ -2,102 +2,65 @@ package com.hithomelabs.princeton1.module4;
 
 import java.util.Iterator;
 
-import javax.annotation.Nonnull;
+public class ArrayQueue<Item> extends Queue<Item> {
 
-public class ArrayQueue<E> extends Queue<E>{
-
-    // insertion from tail, removal from head
-    public static final int DEFAULT_CAPACITY = 10;
-    private int capacity;
-    private int tail;
-    private int head;
-    private int size;
-    private E[] arr;
-
-    public ArrayQueue(){
-        this(DEFAULT_CAPACITY);
-    }
-
-    public ArrayQueue(int capacity){
-        this.capacity = capacity;
-        arr = (E[]) new Object[this.capacity];
-        size = 0;
-    }
+    private int capacity=3;
+    private Item[] arr = (Item[]) new Object[capacity];
+    private int head=0,tail=0;
 
     @Override
     public boolean isEmpty() {
-        return size == 0;
+        return (tail - head) == 0;
+    }
+
+    private void resize(int newCapacity){
+        Item[] temp = arr;
+        arr = (Item[]) new Object[newCapacity];
+        int iNew=0,iOld=head;
+        while(iOld<tail){
+            arr[iNew]=temp[iOld];
+            iNew++;
+            iOld++;
+        }
+
+        capacity=newCapacity;
     }
 
     @Override
-    public E dequeue() {
+    public Item dequeue() {
         if(isEmpty())
             return null;
-        else{
-            E element = arr[head];
-            // Garbage collection
-            arr[head] = null;
-            head = (head+1)%capacity;
-            size = size - 1;
-            if(capacity >= 40 && size < capacity/4){
-                capacity = capacity/2;
-                resize(capacity, capacity*2);
-            }
-            return element;
-        }
+        //        System.out.println(head+" "+arr[head]);
+        Item element = arr[head++];
+        if(size() < capacity/4)
+            resize(capacity/2);
+        return element;
     }
 
     @Override
-    public void enqueue(E element) {
-        // We plan capacity expansion if needed
-        if (size == capacity){
-            capacity = capacity * 2;
-            resize(capacity, capacity/2);
-        }
-        arr[tail] = element;
-        tail = (tail + 1) % capacity;
-        ++size;
-    }
-
-    // When resize takes place always the original array is full, so copy the complete array as is
-    private void resize(int capacity, int oldCapacity) {
-        E[] resizedArr = (E[]) new Object[capacity];
-        for(int i = 0; i < size; i++) {
-            resizedArr[i] = arr[head];
-            // halving because capacity has now doubled
-            arr[head] = null;
-            head = (head + 1) % oldCapacity;
-        }
-        arr = resizedArr;
-        // When resizing takes place, we bring the head to 0 and the tail to size
-        // tail is where new inserts will be made and head will be where elements will be removed
-        tail = size;
-        head = 0;
-
+    public void enqueue(Item element) {
+        if(tail == capacity)
+            resize(capacity * 2);
+        arr[tail++] = element;
     }
 
     @Override
     public int size() {
-        return size;
+        return (tail - head);
     }
 
     @Override
-    @Nonnull
-    public Iterator<E> iterator() {
-        return new Iterator<E>() {
-            int counter = size;
-            int pointer = head;
+    public Iterator<Item> iterator() {
+        return new Iterator<Item>() {
+            int current = head;
             @Override
             public boolean hasNext() {
-                return counter != 0;
+                return current != tail;
             }
 
             @Override
-            public E next() {
-                E element = arr[pointer];
-                pointer = (pointer + 1)% capacity;
-                --counter;
-                return element;
+            public Item next() {
+                return arr[current++];
             }
         };
     }
diff --git a/module4/src/main/java/com/hithomelabs/princeton1/module4/ArrayStack.java b/module4/src/main/java/com/hithomelabs/princeton1/module4/ArrayStack.java
index 93b3f30..8697144 100644
--- a/module4/src/main/java/com/hithomelabs/princeton1/module4/ArrayStack.java
+++ b/module4/src/main/java/com/hithomelabs/princeton1/module4/ArrayStack.java
@@ -1,98 +1,109 @@
 package com.hithomelabs.princeton1.module4;
+
 import java.util.Iterator;
-import javax.annotation.Nonnull;
 
-// Concrete implementation of stack using arrays
-// Creating a generic stack of type E
-public class ArrayStack<E> extends Stack<E> {
+public class ArrayStack<Item> extends Stack<Item>{
 
-    // Capacity and size are two variables, capacity determines total capacity of array, capacity defaults at 10
-    // every time size == capacity, capacity = 2 * capacity
-    private static final int DEFAULT_CAPACITY = 10;
-    private int capacity;
-    private int size;
-    private E[] arr;
+    private int capacity=3;
+    private int top=0;
+    private Item[] arr = (Item[]) new Object[capacity];
 
-    public ArrayStack(int capacity){
-        this.capacity = capacity;
-        arr = (E[]) new Object[this.capacity];
-    }
-
-    // Constructor chaining, default constructor will call parametrized constructor with default initial capacity 10
-    public ArrayStack(){
-        this(DEFAULT_CAPACITY);
-    }
 
     @Override
     public boolean isEmpty() {
-        return size == 0;
+        return top == 0;
     }
 
-    private void changeCapacity(int newCapacity){
-        E[] resizedArr = (E[]) new Object[newCapacity];
-        for (int i = 0; i < size; i++)
-            resizedArr[i] = arr[i];
-        arr = resizedArr;
-    }
+    private void resize(int newCapacity){
+        Item[] temp = arr;
+        arr = (Item[]) new Object[newCapacity];
 
-    private void incrementSize(){
-        if (size == capacity){
-            capacity = 2 * capacity;
-            changeCapacity(capacity);
+        for(int i=0; i<top; i++){
+            arr[i]=temp[i];
         }
-    }
-
-    // Push always happens at the end of the stack
-    // Say the size of the stack is 1, new element gets inserted  at 1
-    @Override
-    public void push(E element) {
-        // Lazy approach, we assume size to always be lesser than capacity
-        incrementSize();
-        arr[size++] = element;
+        capacity=newCapacity;
+//        System.out.println("New Capacity: "+capacity);
     }
 
     @Override
-    public E pop() {
-        if (isEmpty())
+    public void push(Item element) {
+        if(top == capacity)
+            resize(capacity * 2);
+        arr[top++] = element;
+    }
+
+    @Override
+    public Item pop() {
+
+        //System.out.println(top);
+
+        if(top == 0)
+            //throw new java.util.NoSuchElementException();
             return null;
-        else{
-            E e = arr[--size];
-            arr[size] = null;
-            checkResize();
-            return e;
-        }
-    }
 
-    private void checkResize() {
-        if (size < capacity / 4 && capacity >= 20){
-            capacity = capacity / 2;
-            changeCapacity(capacity);
-        }
+        Item element = arr[--top];
+        arr[top] = null;
+
+        if(top < capacity/4)
+            resize(capacity/2);
+        return element;
     }
 
     @Override
     public int size() {
-        return size;
+        return top;
     }
 
     @Override
-    @Nonnull
-    public Iterator<E> iterator() {
-        return new Iterator<E>() {
-
-            int current = 0;
-
+    public Iterator<Item> iterator() {
+        return new Iterator<Item>() {
+            private int current=0;
             @Override
             public boolean hasNext() {
-                return current != size;
+                return current<top;
             }
 
             @Override
-            public E next() {
-                E element = arr[current];
-                current = current + 1;
-                return element;
+            public Item next() {
+                return arr[current++];
             }
         };
     }
+
+    public static void main(String[] args){
+        Stack<Integer> s = new ArrayStack<>();
+
+        try{
+            s.push(0);
+            s.push(1);
+            s.push(2);
+            s.push(3);
+            s.push(4);
+            s.push(5);
+            s.push(6);
+            s.push(7);
+
+            for(Integer i: s)
+                System.out.println(i);
+
+            s.pop();
+            s.pop();
+            s.pop();
+            s.pop();
+            s.pop();
+            s.pop();
+            s.pop();
+            s.pop();
+//            s.pop();
+
+            for(Integer i: s)
+                System.out.println(i);
+
+        } catch (java.util.NoSuchElementException e) {
+            System.out.println("Cannot pop an empty stack");
+        }
+
+
+
+    }
 }
diff --git a/module4/src/main/java/com/hithomelabs/princeton1/module4/Deque.java b/module4/src/main/java/com/hithomelabs/princeton1/module4/Deque.java
new file mode 100644
index 0000000..e0bacf2
--- /dev/null
+++ b/module4/src/main/java/com/hithomelabs/princeton1/module4/Deque.java
@@ -0,0 +1,136 @@
+package com.hithomelabs.princeton1.module4;
+
+
+import java.util.Iterator;
+
+public class Deque<Item> implements Iterable<Item> {
+
+    private Node head;
+    private Node tail;
+    private int capacity;
+
+    private class Node{
+        Item value;
+        Node next;
+    }
+
+    public Deque(){
+        this.head = null;
+        this.tail = null;
+        this.capacity = 0;
+    }
+
+    public boolean isEmpty(){
+        return this.capacity == 0;
+    }
+
+    public int size(){
+        return this.capacity;
+    }
+
+
+    public void addFirst(Item item){
+            Node temp=this.head;
+            this.head=new Node();
+            this.head.value = item;
+            this.head.next = temp;
+//            System.out.println(this.isEmpty());
+            if(this.isEmpty())
+                this.tail=this.head;
+            this.capacity++;
+    }
+
+    public void addLast(Item item){
+        Node temp = new Node();
+        temp.value = item;
+        System.out.println(this.isEmpty());
+        if(!this.isEmpty()) {
+            this.tail.next = temp;
+            this.tail = this.tail.next;
+        }
+        else{
+            this.head = temp;
+            this.tail = temp;
+        }
+        this.capacity++;
+    }
+
+    public Item removeFirst(){
+        Item item = this.head.value;
+        this.head=this.head.next;
+        this.capacity--;
+        return item;
+    }
+
+    public Item removeLast(){
+        Item item = this.tail.value;
+        Node temp = this.head;
+
+        if(capacity <= 1){
+            this.tail=null;
+            this.head=null;
+            return item;
+        }
+
+
+        while(temp.next.next != null){
+            temp=temp.next;
+        }
+
+        this.tail=temp;
+        this.tail.next=null;
+        this.capacity--;
+        return item;
+    }
+
+    @Override
+    public Iterator<Item> iterator() {
+
+        return new Iterator<Item>() {
+            private Node current=head;
+            @Override
+            public boolean hasNext() {
+                return this.current != null;
+            }
+
+            @Override
+            public Item next() {
+                Item item = this.current.value;
+                this.current=this.current.next;
+                return item;
+            }
+        };
+    }
+
+    public static void main(String[] args){
+        Deque<String> deque = new Deque<String>();
+
+        deque.addLast("qwe");
+        deque.addFirst("asd");
+        deque.addLast("zxc");
+
+        for(String s: deque){
+            System.out.println(s);
+        }
+
+        deque.addLast("qwess");
+
+        System.out.println();
+
+        for(String s: deque){
+            System.out.println(s);
+        }
+
+        deque.removeFirst();
+        deque.removeLast();
+        deque.removeFirst();
+        deque.removeLast();
+
+        System.out.println();
+
+        for(String s: deque){
+            System.out.println(s);
+        }
+
+    }
+}
diff --git a/module4/src/main/java/com/hithomelabs/princeton1/module4/LinkedQueue.java b/module4/src/main/java/com/hithomelabs/princeton1/module4/LinkedQueue.java
index b7e62ff..5c7c6d1 100644
--- a/module4/src/main/java/com/hithomelabs/princeton1/module4/LinkedQueue.java
+++ b/module4/src/main/java/com/hithomelabs/princeton1/module4/LinkedQueue.java
@@ -1,51 +1,50 @@
 package com.hithomelabs.princeton1.module4;
 
-import javax.annotation.Nonnull;
 import java.util.Iterator;
 
-public class LinkedQueue<E> extends Queue<E>{
-
-    Node head;
-    Node tail;
-    int size;
+public class LinkedQueue<Item> extends Queue<Item>{
+    private Node head = null, tail = null;
+    private int size = 0;
 
     private class Node{
-        E value;
+        Item value;
         Node next;
-
-        Node(E value){
-            this.value = value;
-        }
     }
 
     @Override
     public boolean isEmpty() {
-        return size==0;
+        return size == 0;
     }
 
     @Override
-    public E dequeue() {
-        if(isEmpty())
+    public Item dequeue() {
+        if(size == 0)
+//            throw new java.util.NoSuchElementException();
             return null;
-        E element = head.value;
-        // Only a single element is present
-        if (head == tail){
-            tail = null;
-        }
+
+        Item element = head.value;
         head = head.next;
-        --size;
+        size--;
+        if(isEmpty())
+            tail=head;
         return element;
     }
 
     @Override
-    public void enqueue(E element) {
-        Node newNode = new Node(element);
-        if(isEmpty())
-            head = newNode;
-        else
+    public void enqueue(Item element) {
+        Node newNode = new Node();
+        newNode.value = element;
+        newNode.next = null;
+        if(isEmpty()){
+            tail=newNode;
+            head=tail;
+        }
+        else{
             tail.next = newNode;
-        tail = newNode;
-        ++size;
+            tail = tail.next;
+        }
+        size++;
+
     }
 
     @Override
@@ -54,9 +53,8 @@ public class LinkedQueue<E> extends Queue<E>{
     }
 
     @Override
-    @Nonnull
-    public Iterator<E> iterator() {
-        return new Iterator<E>() {
+    public Iterator<Item> iterator() {
+        return new Iterator<Item>() {
             Node current = head;
             @Override
             public boolean hasNext() {
@@ -64,11 +62,42 @@ public class LinkedQueue<E> extends Queue<E>{
             }
 
             @Override
-            public E next() {
-                E element = current.value;
+            public Item next() {
+                Item element = current.value;
                 current = current.next;
                 return element;
             }
         };
+
+    }
+
+    public static void main(String[] args){
+        Queue<Integer> q = new LinkedQueue<>();
+
+        try{
+            System.out.println("Queue empty?: " + q.isEmpty());
+            q.enqueue(1);
+            q.enqueue(2);
+            q.enqueue(3);
+            q.enqueue(4);
+
+            for(int value: q)
+                System.out.println(value);
+
+            System.out.println("Queue empty?: " + q.isEmpty());
+            System.out.println("Queue Size?: " + q.size());
+
+            q.dequeue();
+            q.dequeue();
+//            q.dequeue();
+//            q.dequeue();
+//            q.dequeue();
+
+            for(int value: q)
+                System.out.println(value);
+
+        } catch (java.util.NoSuchElementException e) {
+            System.out.println("Cannot dequeue empty queue");
+        }
     }
 }
diff --git a/module4/src/main/java/com/hithomelabs/princeton1/module4/LinkedStack.java b/module4/src/main/java/com/hithomelabs/princeton1/module4/LinkedStack.java
index 6c7c398..73efa56 100644
--- a/module4/src/main/java/com/hithomelabs/princeton1/module4/LinkedStack.java
+++ b/module4/src/main/java/com/hithomelabs/princeton1/module4/LinkedStack.java
@@ -1,72 +1,86 @@
 package com.hithomelabs.princeton1.module4;
+
 import java.util.Iterator;
 
-// Creating a concrete linked Implementation of Stack
-public class LinkedStack<E> extends Stack<E>{
+public class LinkedStack<Item> extends Stack<Item> {
 
-    // No need for an explicit constructor as size will be initialized to 0 and root to null
-    private int size;
-    private Node first;
+    private Node top = null;
+    private int size = 0;
 
-    // By default instance variables are package private
     private class Node{
-        E value;
+        Item value;
         Node next;
     }
 
-    // Will return true if size is 0
+
     @Override
     public boolean isEmpty() {
-        return (this.size == 0);
+        return size == 0 ;
     }
 
-    // Adds an element to the start of a linked list
     @Override
-    public void push(E element) {
+    public void push(Item element) {
         Node newNode = new Node();
         newNode.value = element;
-        newNode.next = first;
-        first = newNode;
-        this.size = this.size + 1;
+        newNode.next = top;
+        top = newNode;
+//        System.out.println(top.value);
+        size++;
     }
 
     @Override
-    public E pop() {
-        if (this.isEmpty())
-            return null;
-        else{
-            Node toBePopped = first;
-            first = first.next;
-            this.size = this.size - 1;
-            return toBePopped.value;
+    public Item pop() {
+        if(size == 0){
+            throw new java.util.NoSuchElementException();
         }
+        Item element = top.value;
+        top=top.next;
+        size--;
+
+        return element;
     }
 
     @Override
     public int size() {
-        return this.size;
+        return size;
     }
 
     @Override
-    public Iterator<E> iterator() {
-        return new Iterator<E>() {
-
-            // Internal classes can access outer objects
-            Node current = first;
+    public Iterator<Item> iterator() {
+        return new Iterator<Item>() {
+            private Node current = top;
             @Override
             public boolean hasNext() {
                 return current != null;
             }
 
             @Override
-            public E next() {
-                E element = current.value;
-                current = current.next;
+            public Item next() {
+                Item element = current.value;
+                current=current.next;
                 return element;
             }
         };
     }
 
+    public static void main(String[] args){
+        Stack <String> s = new LinkedStack<>();
 
+        try {
+            System.out.println("String empty?: " + s.isEmpty());
+//            s.pop();
+            s.push("12");
+            s.push("13");
+            s.pop();
+            s.push("14");
+            System.out.println("String empty?: " + s.isEmpty());
+            System.out.println("String size?: " + s.size());
 
+            for(String value: s){
+                System.out.print(value+" ");
+            }
+        } catch (Exception e) {
+            System.out.println("Cannot pop an empty stack");
+        }
+    }
 }