Sort


1   /*
2    * EJTools, the Enterprise Java Tools
3    *
4    * Distributable under LGPL license.
5    * See terms of license at www.gnu.org.
6    */
7   package org.ejtools.beans;
8   
9   import java.beans.PropertyDescriptor  ;
10  import java.lang.reflect.Method  ;
11  import java.util.Collections  ;
12  import java.util.Comparator  ;
13  import java.util.Iterator  ;
14  import java.util.Vector  ;
15  
16  /**
17   * Utility class that provides different kind of sort strategies for Iterator.
18   *
19   * @author    Laurent Etiemble
20   * @version   $Revision: 1.7 $
21   */
22  public class Sort
23  {
24     /** Constructor for the Sort object */
25     private Sort() { }
26  
27  
28     /**
29      * Extract the elements of the specified class from the Iterator.
30      *
31      * @param iterator  Iterator to scan
32      * @param clazz     Class used for the extraction
33      * @return          The elements of the specified class
34      */
35     public static Iterator   getChildrenByClass(Iterator   iterator, Class   clazz)
36     {
37        Object   object;
38        Vector   vector = new Vector  ();
39  
40        while (iterator.hasNext())
41        {
42           // Check if the object is instance of class
43           if (clazz.isAssignableFrom((object = iterator.next()).getClass()))
44           {
45              vector.addElement(object);
46           }
47        }
48  
49        // Return the result
50        return vector.iterator();
51     }
52  
53  
54     /**
55      * Sort the iterator by class name
56      *
57      * @param iterator  Iterator to sort
58      * @return          The iterator sorted
59      */
60     public static Iterator   sortByClass(Iterator   iterator)
61     {
62        // Create a vector from the iterator
63        Vector   vector = new Vector  ();
64        while (iterator.hasNext())
65        {
66           vector.addElement(iterator.next());
67        }
68  
69        // Apply the comparator
70        Collections.sort(vector,
71           new Comparator  ()
72           {
73              // Compare by class name
74              public int compare(Object   o1, Object   o2)
75              {
76                 return o1.getClass().getName().compareTo(o2.getClass().getName());
77              }
78  
79  
80              public boolean equals(Object   obj)
81              {
82                 return true;
83                 // Ever called?
84              }
85           });
86  
87        // Return the result
88        return vector.iterator();
89     }
90  
91  
92     /**
93      * Sort the iterator by class name and by toString method
94      *
95      * @param iterator  Iterator to sort
96      * @return          The iterator sorted
97      */
98     public static Iterator   sortByClassAndName(Iterator   iterator)
99     {
100       // Create a vector from the iterator
101       Vector   vector = new Vector  ();
102       while (iterator.hasNext())
103       {
104          vector.addElement(iterator.next());
105       }
106 
107       // Apply the comparator
108       Collections.sort(vector,
109          new Comparator  ()
110          {
111             public int compare(Object   o1, Object   o2)
112             {
113                int ret = o1.getClass().getName().compareTo(o2.getClass().getName());
114                if (ret == 0)
115                {
116                   ret = o1.toString().compareTo(o2.toString());
117                }
118                return ret;
119             }
120 
121 
122             public boolean equals(Object   obj)
123             {
124                return true;
125                // Ever called?
126             }
127          });
128 
129       // Return the result
130       return vector.iterator();
131    }
132 
133 
134    /**
135     * Sort the iterator by toString method
136     *
137     * @param iterator  Iterator to sort
138     * @return          The iterator sorted
139     */
140    public static Iterator   sortByName(Iterator   iterator)
141    {
142       // Create a vector from the iterator
143       Vector   vector = new Vector  ();
144       while (iterator.hasNext())
145       {
146          vector.addElement(iterator.next());
147       }
148 
149       // Apply the comparator
150       Collections.sort(vector,
151          new Comparator  ()
152          {
153             public int compare(Object   o1, Object   o2)
154             {
155                return o1.toString().compareTo(o2.toString());
156             }
157 
158 
159             public boolean equals(Object   obj)
160             {
161                return true;
162                // Ever called?
163             }
164          });
165 
166       // Return the result
167       return vector.iterator();
168    }
169 
170 
171    /**
172     * Sort and iterator of JavaBeans by comparing the given property
173     *
174     * @param iterator      Iterator to sort
175     * @param clazz         The class of the JavaBean
176     * @param propertyName  The property used for sorting
177     * @return              The iterator sorted
178     */
179    public static Iterator   sortByProperty(Iterator   iterator, Class   clazz, String   propertyName)
180    {
181       // Create a vector from the iterator
182       Vector   vector = new Vector  ();
183       while (iterator.hasNext())
184       {
185          vector.addElement(iterator.next());
186       }
187 
188       try
189       {
190          // Create the descriptor of the getter
191          final PropertyDescriptor   pd = new PropertyDescriptor  (propertyName, clazz);
192          final Method   m = pd.getReadMethod();
193 
194          // Apply the comparator
195          Collections.sort(vector,
196             new Comparator  ()
197             {
198                public int compare(Object   o1, Object   o2)
199                {
200                   Comparable   val1;
201                   Comparable   val2;
202 
203                   try
204                   {
205                      val1 = (Comparable  ) m.invoke(o1, new Object  [0]);
206                      val2 = (Comparable  ) m.invoke(o2, new Object  [0]);
207                   }
208                   catch (Exception   e)
209                   {
210                      return 0;
211                   }
212 
213                   if (val1 == null)
214                   {
215                      return -1;
216                   }
217                   if (val2 == null)
218                   {
219                      return 1;
220                   }
221 
222                   try
223                   {
224                      return val1.compareTo(val2);
225                   }
226                   catch (Exception   e)
227                   {
228                      // Ignore it
229                   }
230                   return 0;
231                }
232 
233 
234                public boolean equals(Object   obj)
235                {
236                   return true;
237                   // Ever called?
238                }
239             });
240       }
241       catch (Exception   e)
242       {
243          // Ignore it
244       }
245 
246       // Return the result
247       return vector.iterator();
248    }
249 }
250 
251
A to Z: JavaDoc & Examples Daily Java News & Articles Open Source Projects Open Source Codes Free Computer Books Remove Frame
Popular Tags