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Java > Open Source Codes > smallsql > database > ExpressionFunctionRand


1 /* =============================================================
2  * SmallSQL : a free Java DBMS library for the Java(tm) platform
3  * =============================================================
4  *
5  * (C) Copyright 2004-2006, by Volker Berlin.
6  *
7  * Project Info: http://www.smallsql.de/
8  *
9  * This library is free software; you can redistribute it and/or modify it
10  * under the terms of the GNU Lesser General Public License as published by
11  * the Free Software Foundation; either version 2.1 of the License, or
12  * (at your option) any later version.
13  *
14  * This library is distributed in the hope that it will be useful, but
15  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
16  * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
17  * License for more details.
18  *
19  * You should have received a copy of the GNU Lesser General Public
20  * License along with this library; if not, write to the Free Software
21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
22  * USA.
23  *
24  * [Java is a trademark or registered trademark of Sun Microsystems, Inc.
25  * in the United States and other countries.]
26  *
27  * ---------------
28  * ExpressionFunctionRand.java
29  * ---------------
30  * Author: Volker Berlin
31  *
32  */
33 package smallsql.database;
34
35 import java.util.Random JavaDoc;
36
37
38 final class ExpressionFunctionRand extends ExpressionFunctionReturnFloat {
39
40     final static private Random JavaDoc random = new Random JavaDoc();
41     
42     
43     final int getFunction(){ return SQLTokenizer.RAND; }
44     
45
46     boolean isNull() throws Exception JavaDoc{
47         return getParams().length == 1 && param1.isNull();
48     }
49     
50
51     final double getDouble() throws Exception JavaDoc{
52         if(getParams().length == 0)
53             return random.nextDouble();
54         if(isNull()) return 0;
55         return new Random JavaDoc(param1.getLong()).nextDouble();
56     }
57 }
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