/**
 * Copyright 2009 KaChing Group Inc. Licensed 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 com.kaching.platform.common.values;

import static com.google.common.base.Preconditions.checkNotNull;

/**
 * Abstract class providing the skeleton to create type-safe identifiers. This
 * class implements {@link #hashCode()}, {@link #equals(Object)},
 * {@link #toString()} and {@link Comparable#compareTo(Object)}.
 * 
 * A typical use of this class is to introduce a marker type for a specific
 * identifier. In the following example, we are introducing a {@code PersonId}
 * which wraps a long.
<pre>
class PersonId extends AbstractIdentifier&lt;Long&gt; {
  public PersonId(long id) {
    super(id);
  }
}</pre>
 * Using such identifiers makes it possible to have the compiler ensure these
 * identifiers are used consistently.
 * 
 * @param <I> the type of the wrapped identifier
 */
public abstract class AbstractIdentifier<I extends Comparable<I>>
    implements Comparable<AbstractIdentifier<I>> {
  
  private final I id;

  /**
   * Creates an identifier.
   * @param id the wrapped identifier
   */
  protected AbstractIdentifier(I id) {
    this.id = checkNotNull(id);
  }
  
  /**
   * Gets the wrapped identifier.
   * @return the wrapped identifier
   */
  public I getId() {
    return id;
  }
  
  @Override
  @SuppressWarnings("unchecked")
  public boolean equals(Object that) {
    if (this == that) {
      return true;
    }
    if (this.getClass().equals(that.getClass())) {
      return this.getId().equals(((AbstractIdentifier) that).getId());
    } else {
      return false;
    }
  }
  
  @Override
  public int compareTo(AbstractIdentifier<I> that) {
    return this.getId().compareTo(that.getId());
  }
  
  @Override
  public int hashCode() {
    return id.hashCode();
  }
  
  @Override
  public String toString() {
    return id.toString();
  }
  
}

@@ -688,16 +688,46 @@
 tNull;%0A%0A
+import java.io.Serializable;%0A%0A
 /**%0A * A
@@ -1470,20 +1470,16 @@
 able%3CI%3E%3E
-%0A   
  impleme
@@ -1481,16 +1481,20 @@
 plements
+%0A   
  Compara
@@ -1519,18 +1519,104 @@
 fier%3CI%3E%3E
- %7B
+, Serializable %7B%0A  %0A  private static final long serialVersionUID = 8147623822365809694L;
 %0A  %0A  pr

Can't hurt to be serializable and people can use it in more contexts.