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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  
18  package org.apache.commons.math.random;
19  
20  /** 
21   * This class implements a normalized uniform random generator.
22   * <p>Since it is a normalized random generator, it generates values
23   * from a uniform distribution with mean equal to 0 and standard 
24   * deviation equal to 1. Generated values fall in the range
25   * [-&#x0221A;3, +&#x0221A;3].</p>
26   * 
27   * @since 1.2
28   * 
29   * @version $Revision: 754765 $ $Date: 2009-03-15 17:35:38 -0400 (Sun, 15 Mar 2009) $
30   */
31  
32  public class UniformRandomGenerator implements NormalizedRandomGenerator {
33  
34      /** Serializable version identifier. */
35      private static final long serialVersionUID = 1569292426375546027L;
36  
37      /** Create a new generator.
38       * @param generator underlying random generator to use
39       */
40      public UniformRandomGenerator(RandomGenerator generator) {
41          this.generator = generator;
42      }
43  
44      /** Generate a random scalar with null mean and unit standard deviation.
45       * <p>The number generated is uniformly distributed between -&sqrt;(3)
46       * and +&sqrt;(3).</p>
47       * @return a random scalar with null mean and unit standard deviation
48       */
49      public double nextNormalizedDouble() {
50          return SQRT3 * (2 * generator.nextDouble() - 1.0);
51      }
52  
53      /** Underlying generator. */
54      private RandomGenerator generator;
55  
56      /** Square root of three. */
57      private static final double SQRT3 = Math.sqrt(3.0);
58  
59  }