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Java > Open Source Codes > org > apache > velocity > util > SimplePool


1 package org.apache.velocity.util;
2
3 /*
4  * Copyright 1999-2001,2004 The Apache Software Foundation.
5  *
6  * Licensed under the Apache License, Version 2.0 (the "License");
7  * you may not use this file except in compliance with the License.
8  * You may obtain a copy of the License at
9  *
10  * http://www.apache.org/licenses/LICENSE-2.0
11  *
12  * Unless required by applicable law or agreed to in writing, software
13  * distributed under the License is distributed on an "AS IS" BASIS,
14  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15  * See the License for the specific language governing permissions and
16  * limitations under the License.
17  */
18
19 /**
20  * Simple object pool. Based on ThreadPool and few other classes
21  *
22  * The pool will ignore overflow and return null if empty.
23  *
24  * @author Gal Shachor
25  * @author Costin
26  * @author <a HREF="mailto:geirm@optonline.net">Geir Magnusson Jr.</a>
27  * @version $Id: SimplePool.java,v 1.2.14.1 2004/03/03 23:23:07 geirm Exp $
28  */
29 public final class SimplePool
30 {
31     /*
32      * Where the objects are held.
33      */
34     private Object JavaDoc pool[];
35
36     /**
37      * max amount of objects to be managed
38      * set via CTOR
39      */
40     private int max;
41     
42     /**
43      * index of previous to next
44      * free slot
45      */
46     private int current=-1;
47        
48     public SimplePool(int max)
49     {
50         this.max = max;
51         pool = new Object JavaDoc[max];
52     }
53
54     /**
55      * Add the object to the pool, silent nothing if the pool is full
56      */
57     public void put(Object JavaDoc o)
58     {
59         int idx=-1;
60      
61         synchronized( this )
62         {
63             /*
64              * if we aren't full
65              */
66
67             if( current < max - 1 )
68             {
69                 /*
70                  * then increment the
71                  * current index.
72                  */
73                 idx = ++current;
74             }
75
76             if( idx >= 0 )
77             {
78                 pool[idx] = o;
79             }
80         }
81     }
82
83     /**
84      * Get an object from the pool, null if the pool is empty.
85      */
86     public Object JavaDoc get()
87     {
88         int idx = -1;
89         
90         synchronized( this )
91         {
92             /*
93              * if we have any in the pool
94              */
95             if( current >= 0 )
96             {
97                 /*
98                  * take one out, so to speak -
99                  * separate the two operations
100                  * to make it clear that you
101                  * don't want idx = --current; :)
102                  */
103
104                 idx = current;
105                 current--;
106                
107                 /*
108                  * and since current was >= 0
109                  * to get in here, idx must be as well
110                  * so save the if() opration
111                  */
112
113                 return pool[idx];
114             }
115         }
116         
117         return null;
118     }
119
120     /** Return the size of the pool
121      */
122     public int getMax()
123     {
124         return max;
125     }
126 }
127
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