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.List;/** * This {@link IndexDeletionPolicy} implementation that * keeps only the most recent commit and immediately removes * all prior commits after a new commit is done.  This is * the default deletion policy. */public final class KeepOnlyLastCommitDeletionPolicy implements IndexDeletionPolicy {  /**   * Deletes all commits except the most recent one.   */  public void onInit(List commits) {    // Note that commits.size() should normally be 1:    onCommit(commits);  }  /**   * Deletes all commits except the most recent one.   */  public void onCommit(List commits) {    // Note that commits.size() should normally be 2 (if not    // called by onInit above):    int size = commits.size();    for(int i=0;i<size-1;i++) {      ((IndexCommit) commits.get(i)).delete();    }  }}