RandomFactory.java revision 2638:d14008abb551 
1/*
2 * Copyright (c) 2015, 2017, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 */
23
24package jdk.test.lib;
25
26import java.util.Random;
27import java.util.SplittableRandom;
28
29/**
30 * Factory class which generates and prints to STDOUT a long-valued seed
31 * for use in initializing a PRNG.  An instance of {@code Random} or
32 * {@code SplittableRandom} may likewise be obtained.
33 */
34public class RandomFactory {
35    /**
36     * Attempt to obtain the seed from the value of the "seed" property.
37     * @return The seed or {@code null} if the "seed" property was not set or
38     *         could not be parsed.
39     */
40    private static Long getSystemSeed() {
41        Long seed = null;
42        try {
43            // note that Long.valueOf(null) also throws a
44            // NumberFormatException so if the property is undefined this
45            // will still work correctly
46            seed = Long.valueOf(System.getProperty("seed"));
47        } catch (NumberFormatException e) {
48            // do nothing: seed is still null
49        }
50
51        return seed;
52    }
53
54    /**
55     * Obtain a seed from an independent PRNG.
56     *
57     * @return A random seed.
58     */
59    private static long getRandomSeed() {
60        return new Random().nextLong();
61    }
62
63    /**
64     * Obtain and print to STDOUT a seed appropriate for initializing a PRNG.
65     * If the system property "seed" is set and has value which may be correctly
66     * parsed it is used, otherwise a seed is generated using an independent
67     * PRNG.
68     *
69     * @return The seed.
70     */
71    public static long getSeed() {
72        Long seed = getSystemSeed();
73        if (seed == null) {
74            seed = getRandomSeed();
75        }
76        System.out.println("Seed from RandomFactory = "+seed+"L");
77        return seed;
78    }
79
80    /**
81     * Obtain and print to STDOUT a seed and use it to initialize a new
82     * {@code Random} instance which is returned. If the system
83     * property "seed" is set and has value which may be correctly parsed it
84     * is used, otherwise a seed is generated using an independent PRNG.
85     *
86     * @return The {@code Random} instance.
87     */
88    public static Random getRandom() {
89        return new Random(getSeed());
90    }
91
92    /**
93     * Obtain and print to STDOUT a seed and use it to initialize a new
94     * {@code SplittableRandom} instance which is returned. If the system
95     * property "seed" is set and has value which may be correctly parsed it
96     * is used, otherwise a seed is generated using an independent PRNG.
97     *
98     * @return The {@code SplittableRandom} instance.
99     */
100    public static SplittableRandom getSplittableRandom() {
101        return new SplittableRandom(getSeed());
102    }
103}
104