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diff --git a/lucene-java-3.5.0/lucene/src/java/org/apache/lucene/store/SingleInstanceLockFactory.java b/lucene-java-3.5.0/lucene/src/java/org/apache/lucene/store/SingleInstanceLockFactory.java
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+++ b/lucene-java-3.5.0/lucene/src/java/org/apache/lucene/store/SingleInstanceLockFactory.java
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+package org.apache.lucene.store;
+
+/**
+ * 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.
+ */
+
+import java.io.IOException;
+import java.util.HashSet;
+
+/**
+ * Implements {@link LockFactory} for a single in-process instance,
+ * meaning all locking will take place through this one instance.
+ * Only use this {@link LockFactory} when you are certain all
+ * IndexReaders and IndexWriters for a given index are running
+ * against a single shared in-process Directory instance.  This is
+ * currently the default locking for RAMDirectory.
+ *
+ * @see LockFactory
+ */
+
+public class SingleInstanceLockFactory extends LockFactory {
+
+  private HashSet<String> locks = new HashSet<String>();
+
+  @Override
+  public Lock makeLock(String lockName) {
+    // We do not use the LockPrefix at all, because the private
+    // HashSet instance effectively scopes the locking to this
+    // single Directory instance.
+    return new SingleInstanceLock(locks, lockName);
+  }
+
+  @Override
+  public void clearLock(String lockName) throws IOException {
+    synchronized(locks) {
+      if (locks.contains(lockName)) {
+        locks.remove(lockName);
+      }
+    }
+  }
+}
+
+class SingleInstanceLock extends Lock {
+
+  String lockName;
+  private HashSet<String> locks;
+
+  public SingleInstanceLock(HashSet<String> locks, String lockName) {
+    this.locks = locks;
+    this.lockName = lockName;
+  }
+
+  @Override
+  public boolean obtain() throws IOException {
+    synchronized(locks) {
+      return locks.add(lockName);
+    }
+  }
+
+  @Override
+  public void release() {
+    synchronized(locks) {
+      locks.remove(lockName);
+    }
+  }
+
+  @Override
+  public boolean isLocked() {
+    synchronized(locks) {
+      return locks.contains(lockName);
+    }
+  }
+
+  @Override
+  public String toString() {
+    return super.toString() + ": " + lockName;
+  }
+}