1 files changed, 131 insertions, 0 deletions
diff --git a/qpid/java/junit-toolkit/src/main/org/apache/qpid/junit/extensions/util/StackQueue.java b/qpid/java/junit-toolkit/src/main/org/apache/qpid/junit/extensions/util/StackQueue.java
new file mode 100644
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--- /dev/null
+++ b/qpid/java/junit-toolkit/src/main/org/apache/qpid/junit/extensions/util/StackQueue.java
@@ -0,0 +1,131 @@
+/*
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ *
+ */
+package org.apache.qpid.junit.extensions.util;
+
+import java.util.EmptyStackException;
+import java.util.NoSuchElementException;
+import java.util.Queue;
+import java.util.Stack;
+
+/**
+ * The Stack class in java.util (most unhelpfully) does not implement the Queue interface. This is an adaption of that
+ * class as a queue.
+ *
+ * <p><table id="crc"><caption>CRC Card</caption>
+ * <tr><th> Responsibilities <th> Collaborations
+ * <tr><td> Turn a stack into a queue.
+ * </table>
+ *
+ * @todo Need to override the add method, and iterator and consider other methods too. They work like LIFO but
+ *       really wany FIFO behaviour accross the whole data structure.
+ *
+ * @author Rupert Smith
+ */
+public class StackQueue<E> extends Stack<E> implements Queue<E>
+{
+    /**
+     * Retrieves, but does not remove, the head of this queue.
+     *
+     * @return The element at the top of the stack.
+     */
+    public E element()
+    {
+        try
+        {
+            return super.peek();
+        }
+        catch (EmptyStackException e)
+        {
+            NoSuchElementException t = new NoSuchElementException();
+            t.initCause(e);
+            throw t;
+        }
+    }
+
+    /**
+     * Inserts the specified element into this queue, if possible.
+     *
+     * @param o The data element to push onto the stack.
+     *
+     * @return True if it was added to the stack, false otherwise (this implementation always returns true).
+     */
+    public boolean offer(E o)
+    {
+        push(o);
+
+        return true;
+    }
+
+    /**
+     * Retrieves, but does not remove, the head of this queue, returning null if this queue is empty.
+     *
+     * @return The top element from the stack, or null if the stack is empty.
+     */
+    public E peek()
+    {
+        try
+        {
+            return super.peek();
+        }
+        catch (EmptyStackException e)
+        {
+            return null;
+        }
+    }
+
+    /**
+     * Retrieves and removes the head of this queue, or null if this queue is empty.
+     *
+     * @return The top element from the stack, or null if the stack is empty.
+     */
+    public E poll()
+    {
+        try
+        {
+            return super.pop();
+        }
+        catch (EmptyStackException e)
+        {
+            return null;
+        }
+    }
+
+    /**
+     * Retrieves and removes the head of this queue.
+     *
+     * @return The top element from the stack, or null if the stack is empty.
+     *
+     * @throws NoSuchElementException If the stack is empty so no element can be removed from it.
+     */
+    public E remove()
+    {
+        try
+        {
+            return super.pop();
+        }
+        catch (EmptyStackException e)
+        {
+            NoSuchElementException t = new NoSuchElementException();
+            t.initCause(e);
+            throw t;
+        }
+    }
+}