java/src/main/com/google/appengine/api/datastore/Category.java

   1 /*
   2  * Copyright 2009 Google Inc.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License"); you may not
   5  * use this file except in compliance with the License. You may obtain a copy of
   6  * the License at
   7  *
   8  * http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
  12  * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
  13  * License for the specific language governing permissions and limitations under
  14  * the License.
  15  */
  16 package com.google.appengine.api.datastore;
  17
  18 import java.io.Serializable;
  19
  20 /**
  21  * A tag, ie a descriptive word or phrase. Entities may be tagged by users,
  22  * and later returned by a queries for that tag. Tags can also be used for
  23  * ranking results (frequency), photo captions, clustering, activity, etc.
  24  *
  25  * @see <a href="http://www.zeldman.com/daily/0405d.shtml">Jeffrey Zeldmans blog post</a>
  26  * on tag clouds for a more in-depth description.
  27  */
  28 public final class Category implements Serializable, Comparable<Category> {
  29
  30   public static final long serialVersionUID = 8556134984576082397L;
  31
  32   private String category;
  33
  34   public Category(String category) {
  35     if (category == null) {
  36       throw new NullPointerException("category must not be null");
  37     }
  38     this.category = category;
  39   }
  40
  41   /**
  42    * This constructor exists for frameworks (e.g. Google Web Toolkit)
  43    * that require it for serialization purposes.  It should not be
  44    * called explicitly.
  45    */
  46   @SuppressWarnings("unused")
  47   private Category() {
  48     this.category = null;
  49   }
  50
  51   public String getCategory() {
  52     return category;
  53   }
  54
  55   @Override
  56   public int compareTo(Category o) {
  57     return category.compareTo(o.category);
  58   }
  59
  60   @Override
  61   public boolean equals(Object o) {
  62     if (this == o) {
  63       return true;
  64     }
  65     if (o == null || getClass() != o.getClass()) {
  66       return false;
  67     }
  68
  69     Category category1 = (Category) o;
  70
  71     if (!category.equals(category1.category)) {
  72       return false;
  73     }
  74
  75     return true;
  76   }
  77
  78   @Override
  79   public int hashCode() {
  80     return category.hashCode();
  81   }
  82 }