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src/main/java/com/google/code/yanf4j/util/ConcurrentHashSet.java

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+/**
+ * Copyright [2009-2010] [dennis zhuang(killme2008@gmail.com)] Licensed 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
+ */
+/**
+ * Copyright [2009-2010] [dennis zhuang(killme2008@gmail.com)] Licensed 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 com.google.code.yanf4j.util;
+
+import java.util.Collection;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentMap;
+
+/**
+ * A {@link ConcurrentHashMap}-backed {@link Set}.
+ * 
+ * @author The Apache MINA Project (dev@mina.apache.org)
+ * @version $Rev: 597692 $, $Date: 2007-11-23 08:56:32 -0700 (Fri, 23 Nov 2007) $
+ */
+public class ConcurrentHashSet<E> extends MapBackedSet<E> {
+
+  private static final long serialVersionUID = 8518578988740277828L;
+
+  public ConcurrentHashSet() {
+    super(new ConcurrentHashMap<E, Boolean>());
+  }
+
+  public ConcurrentHashSet(Collection<E> c) {
+    super(new ConcurrentHashMap<E, Boolean>(), c);
+  }
+
+  @Override
+  public boolean add(E o) {
+    Boolean answer = ((ConcurrentMap<E, Boolean>) map).putIfAbsent(o, Boolean.TRUE);
+    return answer == null;
+  }
+}