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 locks = new HashSet();  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);  }  public void clearLock(String lockName) throws IOException {    synchronized(locks) {      if (locks.contains(lockName)) {        locks.remove(lockName);      }    }  }};class SingleInstanceLock extends Lock {  String lockName;  private HashSet locks;  public SingleInstanceLock(HashSet locks, String lockName) {    this.locks = locks;    this.lockName = lockName;  }  public boolean obtain() throws IOException {    synchronized(locks) {      return locks.add(lockName);    }  }  public void release() {    synchronized(locks) {      locks.remove(lockName);    }  }  public boolean isLocked() {    synchronized(locks) {      return locks.contains(lockName);    }  }  public String toString() {      return "SingleInstanceLock: " + lockName;  }}