X-Git-Url: https://git.opendaylight.org/gerrit/gitweb?p=controller.git;a=blobdiff_plain;f=opendaylight%2Fmd-sal%2Fcds-access-client%2Fsrc%2Fmain%2Fjava%2Forg%2Fopendaylight%2Fcontroller%2Fcluster%2Faccess%2Fclient%2FEmptyQueue.java;fp=opendaylight%2Fmd-sal%2Fcds-access-client%2Fsrc%2Fmain%2Fjava%2Forg%2Fopendaylight%2Fcontroller%2Fcluster%2Faccess%2Fclient%2FEmptyQueue.java;h=31d863a36cf8721de52969ed0bfb5e94dfad4922;hp=0000000000000000000000000000000000000000;hb=9b4f21460c6dcb10c381df631d064d05de16546c;hpb=e514a5fc59ade7ac2ce5faf0ba5c75c3cb259c7f

diff --git a/opendaylight/md-sal/cds-access-client/src/main/java/org/opendaylight/controller/cluster/access/client/EmptyQueue.java b/opendaylight/md-sal/cds-access-client/src/main/java/org/opendaylight/controller/cluster/access/client/EmptyQueue.java
new file mode 100644
index 0000000000..31d863a36c
--- /dev/null
+++ b/opendaylight/md-sal/cds-access-client/src/main/java/org/opendaylight/controller/cluster/access/client/EmptyQueue.java
@@ -0,0 +1,60 @@
+/*
+ * Copyright (c) 2016 Cisco Systems, Inc. and others.  All rights reserved.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v1.0 which accompanies this distribution,
+ * and is available at http://www.eclipse.org/legal/epl-v10.html
+ */
+package org.opendaylight.controller.cluster.access.client;
+
+import java.util.AbstractQueue;
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.Queue;
+
+/**
+ * A specialized always-empty implementation of {@link java.util.Queue}. This implementation will always refuse new
+ * elements in its {@link #offer(Object)} method.
+
+ * @author Robert Varga
+ *
+ * @param <E> the type of elements held in this collection
+ */
+// TODO: move this class into yangtools.util
+final class EmptyQueue<T> extends AbstractQueue<T> {
+    private static final EmptyQueue<?> INSTANCE = new EmptyQueue<>();
+
+    private EmptyQueue() {
+        // No instances
+    }
+
+    @SuppressWarnings("unchecked")
+    static <T> Queue<T> getInstance() {
+        return (Queue<T>) INSTANCE;
+    }
+
+    @Override
+    public boolean offer(final T e) {
+        return false;
+    }
+
+    @Override
+    public T poll() {
+        return null;
+    }
+
+    @Override
+    public T peek() {
+        return null;
+    }
+
+    @Override
+    public Iterator<T> iterator() {
+        return Collections.emptyIterator();
+    }
+
+    @Override
+    public int size() {
+        return 0;
+    }
+}
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