Finish AB 2

src/BodyQueue.java

@@ -5,13 +5,20 @@
 //
 public class BodyQueue {
 
-    //TODO: declare variables.
+    private int capacity;
+    private int head = 0;
+    private int tail = 0;
+    private Body[] queue;
+
+    public BodyQueue() {
+        this(4);
+    }
 
     // Initializes this queue with an initial capacity.
     // Precondition: initialCapacity > 0.
     public BodyQueue(int initialCapacity) {
-
-        //TODO: define constructor.
+        this.capacity = initialCapacity;
+        this.queue = new Body[this.capacity];
     }
 
     // Initializes this queue as an independent copy of the specified queue.
@@ -19,28 +26,50 @@ public class BodyQueue {
     // and vice versa.
     // Precondition: q != null.
     public BodyQueue(BodyQueue q) {
-
-        //TODO: define constructor.
+        this.capacity = q.capacity;
+        this.head = q.size();
+        this.tail = 0;
+        this.queue = new Body[this.capacity];
+        for (int i = 0; i < q.size(); i++) {
+            this.queue[i] = q.queue[i];
+        }
     }
 
     // Adds the specified body 'b' to this queue.
     public void add(Body b) {
-
-        //TODO: implement method.
+        queue[head] = b;
+        head = (head + 1) % capacity;
+        if (head == tail) {
+            doubleCapacity();
+            head = capacity / 2;
+        }
     }
 
     // Retrieves and removes the head of this queue, or returns 'null'
     // if this queue is empty.
     public Body poll() {
-
-        //TODO: implement method.
-        return null;
+        if (tail == head) {
+            return null;
+        }
+        Body b = queue[tail];
+        queue[tail] = null;
+        tail = (tail + 1) % capacity;
+        return b;
     }
 
     // Returns the number of bodies in this queue.
     public int size() {
+        return (head - tail + capacity) % capacity;
+    }
 
-        //TODO: implement method.
-        return -1;
+    private void doubleCapacity() {
+        Body[] tmp = new Body[capacity * 2];
+        for (int i = head, j = 0; i < tail + capacity; i++, j++) {
+            tmp[j] = queue[i % capacity];
+        }
+        head = capacity;
+        tail = 0;
+        capacity *= 2;
+        queue = tmp;
     }
 }