module4/src/main/java/com/hithomelabs/princeton1/module4/ArrayQueue.java

@@ -7,12 +7,14 @@ import javax.annotation.Nonnull;
 public class ArrayQueue<E> extends Queue<E>{
 
     private E[] queueArray = (E[]) new Object[1];
-    private int startPtr = 0;
-    private int endPtr = 0;
+    private int startPtr;
+    private int endPtr;
+    private int size;
+    private int queueArrayLength = queueArray.length;
 
     @Override
     public boolean isEmpty() {
-        return startPtr >= endPtr;
+        return size == 0;
     }
 
     @Override
@@ -20,25 +22,27 @@ public class ArrayQueue<E> extends Queue<E>{
         if(isEmpty()){
             return null;
         }
-        E currentValue = queueArray[startPtr];
-        queueArray[startPtr++] = null;
-        if(size() < queueArray.length/4){
-            changeArraySize(queueArray.length/2);
+        E currentValue = queueArray[startPtr % queueArrayLength];
+        queueArray[startPtr++ % queueArrayLength] = null;
+        size--;
+        if(size() < queueArrayLength/4){
+            changeArraySize(queueArrayLength/2);
         }
         return currentValue;
     }
 
     @Override
     public void enqueue(E element) {
-        queueArray[endPtr++] = element;
-        if(endPtr >= queueArray.length){
-            changeArraySize(queueArray.length*2);
+        queueArray[endPtr++ % queueArrayLength] = element;
+        size++;
+        if(size == queueArrayLength){
+            changeArraySize(queueArrayLength*2);
         }
     }
 
     @Override
     public int size() {
-        return endPtr - startPtr;
+        return size;
     }
 
     private void changeArraySize(int targetSize){
@@ -50,6 +54,7 @@ public class ArrayQueue<E> extends Queue<E>{
             queueArray[j++]=tempArray[i];
         endPtr = size();
         startPtr = 0;
+        queueArrayLength = queueArray.length;
     }
 
     @Nonnull