content: package org.apache.lucene.util;
  
  /**
   * 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.ObjectStreamException;
  import java.io.Serializable;
  import java.io.StreamCorruptedException;
  import java.util.HashMap;
  import java.util.Map;
  
  /**
   * A serializable Enum class.
   * @deprecated Use Java 5 enum, will be removed in a later Lucene 3.x release.
   * @lucene.internal
   */
  @Deprecated
  @SuppressWarnings("serial")
  public abstract class Parameter implements Serializable {
    static Map<String,Parameter> allParameters = new HashMap<String,Parameter>();
    
    private String name;
    
    protected Parameter(String name) {
      // typesafe enum pattern, no public constructor
      this.name = name;
      String key = makeKey(name);
      
      if(allParameters.containsKey(key))
        throw new IllegalArgumentException("Parameter name " + key + " already used!");
      
      allParameters.put(key, this);
    }
    
    private String makeKey(String name){
      return getClass() + " " + name;
    }
    
    @Override
    public String toString() {
      return name;
    }
    
    /**
     * Resolves the deserialized instance to the local reference for accurate
     * equals() and == comparisons.
     * 
     * @return a reference to Parameter as resolved in the local VM
     * @throws ObjectStreamException
     */
    protected Object readResolve() throws ObjectStreamException {
      Object par = allParameters.get(makeKey(name));
      
      if(par == null)
        throw new StreamCorruptedException("Unknown parameter value: " + name);
        
      return par;
    }
    
   }
  