content: /*
   *
   * 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.
   *
   */
  package org.apache.bookkeeper.versioning;
  
  /**
   * An interface that allows us to determine if a given version happened before or after another version.
   */
  public interface Version {
  
      /**
       * Initial version.
       */
      Version NEW = new Version() {
          @Override
          public Occurred compare(Version v) {
              if (null == v) {
                  throw new NullPointerException("Version is not allowed to be null.");
              }
              if (this == v) {
                  return Occurred.CONCURRENTLY;
              }
              return Occurred.BEFORE;
          }
      };
  
      /**
       * Match any version.
       */
      Version ANY = v -> {
          if (null == v) {
              throw new NullPointerException("Version is not allowed to be null.");
          }
          return Occurred.CONCURRENTLY;
      };
  
      /**
       * Define the sequence of versions.
       */
      enum Occurred {
          BEFORE, AFTER, CONCURRENTLY
      }
  
      Occurred compare(Version v);
  }
  