my midterm files

src/Main.java

@@ -4,9 +4,14 @@ public static void main(String[] args) {
 
         Deque<String> d1 = new ResizingArrayDeque<>();
         // some test code here
+        d1.addFirst("pink");
+        d1.addFirst("brown");
+        System.out.println(d1.size());
 
         Deque<String> d2 = new SinglyLinkedDeque<>();
         // some test code here
-
+        d2.addFirst("pink");
+        d2.addFirst("brown");
+        System.out.println(d2.size());
     }
 }

src/ResizingArrayDeque.java

@@ -33,9 +33,13 @@ public int size() {
     public void addFirst(ItemType item) {
         // consider the case of adding to an empty list
         // consider the case of adding to a non-empty list
+        if (item == null) {
+            throw new NullPointerException();
+        }
 
         // There is a private helper method checkSize() defined below to check/resize
         // that you can call as needed to check if the array is full and resize it.
+
     }
 
     /**
@@ -47,7 +51,9 @@ public void addFirst(ItemType item) {
     public void addLast(ItemType item) {
         // consider the case of adding to an empty list
         // consider the case of adding to a non-empty list
-
+        if (item == null) {
+            throw new NullPointerException();
+        }
         // There is a private helper method checkSize() defined below to check/resize
         // that you can call as needed to check if the array is full and resize it.
     }
@@ -109,7 +115,7 @@ private void checkSize() {
                 temp[i] = data[i];
             }
 
-            // Step 3 - repoint/refererence data to point to new array
+            // Step 3 - repoint/reference data to point to new array
             data = temp;
 
             // Optional:

src/SinglyLinkedDeque.java

@@ -27,6 +27,7 @@ public int size() {
         return size;
     }
 
+
     /**
      * Adds an item to the front of the deque.
      *
@@ -36,6 +37,10 @@ public int size() {
     public void addFirst(ItemType item) {
         // consider the case of adding to an empty list
         // consider the case of adding to a non-empty list
+        if (item == null) {
+            throw new NullPointerException();
+        }
+
     }
 
     /**
@@ -47,6 +52,7 @@ public void addFirst(ItemType item) {
     public void addLast(ItemType item) {
         // consider the case of adding to an empty list
         // consider the case of adding to a non-empty list
+
     }
 
     /**
@@ -63,6 +69,7 @@ public ItemType removeFirst() {
 
         // if not empty:
         // 0. figure out a way to access the item in the front
+
         // 1. make a variable to save a copy of the item at the front
         // 2. remove the item at the front
         // 3. return the variable that has the saved copy of the item at the front