Implementato alcuni esercizi

esercizi/QStack.java

@@ -0,0 +1,65 @@
+package esercizi;
+
+import exceptions.EmptyStackException;
+import queue.NodeQueue;
+import stack.Stack;
+
+/**
+ * Created with MONSTER.
+ * User: xgiovio
+ * Date: 13/04/2014
+ * Time: 23:48
+ */
+
+// emulate a stack with a queue
+public class QStack<E> implements Stack<E> {
+
+    NodeQueue<E> a = new NodeQueue<E>();
+
+    @Override
+    public void push(E element) {
+        a.enqueue(element);
+    }
+
+    @Override
+    public E top() throws EmptyStackException {
+        if (a.isEmpty()){
+            throw new EmptyStackException();
+        }else {
+            E t;
+            for (int i = 0 ;i<a.size() - 1;i++){
+                a.enqueue(a.dequeue());
+            }
+            t = a.front();
+            a.enqueue(a.dequeue());
+            return t;
+        }
+    }
+
+    @Override
+    public E pop() throws EmptyStackException {
+        if (a.isEmpty()){
+            throw new EmptyStackException();
+        }else {
+            for (int i = 0 ;i<a.size() - 1;i++){
+                a.enqueue(a.dequeue());
+            }
+            return a.dequeue();
+        }
+    }
+
+    @Override
+    public boolean isEmpty() {
+        return a.isEmpty();
+    }
+
+    @Override
+    public int size() {
+        return a.size();
+    }
+
+    @Override
+    public String toString() {
+        return a.toString();
+    }
+}