package org.apache.lucene.index;/** * 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.util.Collection;import java.io.IOException;import org.apache.lucene.store.Directory;/** * <p>Expert: represents a single commit into an index as seen by the * {@link IndexDeletionPolicy} or {@link IndexReader}.</p> * * <p> Changes to the content of an index are made visible * only after the writer who made that change commits by * writing a new segments file * (<code>segments_N</code>). This point in time, when the * action of writing of a new segments file to the directory * is completed, is an index commit.</p> * * <p>Each index commit point has a unique segments file * associated with it. The segments file associated with a * later index commit point would have a larger N.</p> * * <p><b>WARNING</b>: This API is a new and experimental and * may suddenly change. </p>*/public abstract class IndexCommit implements IndexCommitPoint {  /**   * Get the segments file (<code>segments_N</code>) associated    * with this commit point.   */  public abstract String getSegmentsFileName();  /**   * Returns all index files referenced by this commit point.   */  public abstract Collection getFileNames() throws IOException;  /**   * Returns the {@link Directory} for the index.   */  public abstract Directory getDirectory();    /**   * Delete this commit point.  This only applies when using   * the commit point in the context of IndexWriter's   * IndexDeletionPolicy.   * <p>   * Upon calling this, the writer is notified that this commit    * point should be deleted.    * <p>   * Decision that a commit-point should be deleted is taken by the {@link IndexDeletionPolicy} in effect   * and therefore this should only be called by its {@link IndexDeletionPolicy#onInit onInit()} or    * {@link IndexDeletionPolicy#onCommit onCommit()} methods.  */  public void delete() {    throw new UnsupportedOperationException("This IndexCommit does not support this method.");  }  public boolean isDeleted() {    throw new UnsupportedOperationException("This IndexCommit does not support this method.");  }  /**   * Returns true if this commit is an optimized index.   */  public boolean isOptimized() {    throw new UnsupportedOperationException("This IndexCommit does not support this method.");  }  /**   * Two IndexCommits are equal if both their Directory and versions are equal.   */  public boolean equals(Object other) {    if (other instanceof IndexCommit) {      IndexCommit otherCommit = (IndexCommit) other;      return otherCommit.getDirectory().equals(getDirectory()) && otherCommit.getVersion() == getVersion();    } else      return false;  }  public int hashCode() {    return getDirectory().hashCode() + getSegmentsFileName().hashCode();  }  /** Returns the version for this IndexCommit.  This is the      same value that {@link IndexReader#getVersion} would      return if it were opened on this commit. */  public long getVersion() {    throw new UnsupportedOperationException("This IndexCommit does not support this method.");  }  /** Returns the generation (the _N in segments_N) for this      IndexCommit */  public long getGeneration() {    throw new UnsupportedOperationException("This IndexCommit does not support this method.");  }  /** Convenience method that returns the last modified time   *  of the segments_N file corresponding to this index   *  commit, equivalent to   *  getDirectory().fileModified(getSegmentsFileName()). */  public long getTimestamp() throws IOException {    return getDirectory().fileModified(getSegmentsFileName());  }}