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Java > Open Source Codes > org > apache > commons > betwixt > io > id > RandomIDGenerator


1 /*
2  * Copyright 2001-2004 The Apache Software Foundation.
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of 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,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 package org.apache.commons.betwixt.io.id;
17
18 import java.util.Random JavaDoc;
19
20 /** <p>Generates <code>ID</code>'s at random.
21   * The random number source is <code>java.util.Random</code>.</p>
22   *
23   * <p>Random <code>ID</code>'s are very useful if you're inserting
24   * elements created by <code>Betwixt</code> into a stream with existing
25   * elements.
26   * Using random <code>ID</code>'s should reduce the danger of collision
27   * with existing element <code>ID</code>'s.</p>
28   *
29   * <p>This class can generate positive-only ids (the default)
30   * or it can generate a mix of negative and postive ones.
31   * This behaviour can be set by {@link #setPositiveIds}
32   * or by using the {@link #RandomIDGenerator(boolean onlyPositiveIds)}
33   * constructor.</p>
34   *
35   * @author <a HREF="mailto:rdonkin@apache.org">Robert Burrell Donkin</a>
36   * @version $Revision: 1.7 $
37   */
38 public final class RandomIDGenerator extends AbstractIDGenerator {
39     
40     /** Use simple java.util.Random as the source for our numbers */
41     private Random JavaDoc random = new Random JavaDoc();
42     /** Should only positive id's be generated? */
43     private boolean onlyPositiveIds = true;
44         
45     /**
46       * Constructor sets the <code>PositiveIds</code> property to <code>true</code>.
47       */
48     public RandomIDGenerator() {}
49     
50     /**
51       * Constructor sets <code>PositiveIds</code> property.
52       *
53       * @param onlyPositiveIds set <code>PositiveIds</code> property to this value
54       */
55     public RandomIDGenerator(boolean onlyPositiveIds) {
56         setPositiveIds(onlyPositiveIds);
57     }
58     
59     /**
60       * <p>Generates a random <code>ID</code><p>
61       *
62       * <p>If the <code>PositiveIds</code> property is true,
63       * then this method will recursively call itself if the random
64       * <code>ID</code> is less than zero.</p>
65       *
66       * @return a random integer (converted to a string)
67       */
68     public String JavaDoc nextIdImpl() {
69         int next = random.nextInt();
70         if (onlyPositiveIds && next<0) {
71             // it's negative and we're ignoring them so get another
72 return nextIdImpl();
73         }
74         return Integer.toString(next);
75     }
76     
77     /**
78      * Gets whether only positive <code>ID</code>'s should be generated
79      *
80      * @return whether only positive IDs should be generated
81      */
82     public boolean getPositiveIds() {
83         return onlyPositiveIds;
84     }
85     
86     /**
87      * Sets whether only positive <code>ID</code>'s should be generated
88      *
89      * @param onlyPositiveIds pass true if only positive IDs should be generated
90      */
91     public void setPositiveIds(boolean onlyPositiveIds) {
92         this.onlyPositiveIds = onlyPositiveIds;
93     }
94 }
95
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