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Java > Open Source Codes > com > sun > enterprise > util > UniqueValueBlock


1 /*
2  * The contents of this file are subject to the terms
3  * of the Common Development and Distribution License
4  * (the License). You may not use this file except in
5  * compliance with the License.
6  *
7  * You can obtain a copy of the license at
8  * https://glassfish.dev.java.net/public/CDDLv1.0.html or
9  * glassfish/bootstrap/legal/CDDLv1.0.txt.
10  * See the License for the specific language governing
11  * permissions and limitations under the License.
12  *
13  * When distributing Covered Code, include this CDDL
14  * Header Notice in each file and include the License file
15  * at glassfish/bootstrap/legal/CDDLv1.0.txt.
16  * If applicable, add the following below the CDDL Header,
17  * with the fields enclosed by brackets [] replaced by
18  * you own identifying information:
19  * "Portions Copyrighted [year] [name of copyright owner]"
20  *
21  * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
22  */
23 package com.sun.enterprise.util;
24
25 import java.io.Serializable JavaDoc;
26
27 /**
28  * Represents a block of unique numbers reserved for a particular
29  * context by the backend value generator. This class should
30  * only be used internally by concrete UniqueValueGenerator implementations.
31  *
32  * @author Kenneth Saks
33  */
34 public class UniqueValueBlock implements Serializable JavaDoc {
35     
36     // Lowest value available
37 private long start_;
38     
39     // Number of values available in this block
40 private long extent_;
41
42     // Current value
43 private long current_;
44
45     /**
46      * Use package-level access since this class should only be
47      * used internally by concrete instances of UniqueValueGenerator.
48      * The extent value must be >= 1.
49      */
50     UniqueValueBlock(long start, long extent) {
51         start_ = start;
52         extent_ = extent;
53         current_ = start;
54     }
55     
56     public synchronized boolean hasNext() {
57         return (current_ < (start_ + extent_));
58     }
59
60     public synchronized long next() {
61         if( !hasNext() ) {
62             throw new IllegalStateException JavaDoc();
63         }
64         long returnValue = current_;
65         current_++;
66         return returnValue;
67     }
68 }
69
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