1 /* 2 * Copyright (c) 2015, 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 24 import java.util.Random; 25 import java.util.SplittableRandom; 26 27 /** 28 * Factory class which generates and prints to STDOUT a long-valued seed 29 * for use in initializing a PRNG. An instance of {@code Random} or 30 * {@code SplittableRandom} may likewise be obtained. 31 */ 32 public class RandomFactory { 33 /** 34 * Attempt to obtain the seed from the value of the "seed" property. 35 * @return The seed or {@code null} if the "seed" property was not set or 36 * could not be parsed. 37 */ 38 private static Long getSystemSeed() { 39 Long seed = null; 40 try { 41 // note that Long.valueOf(null) also throws a 42 // NumberFormatException so if the property is undefined this 43 // will still work correctly 44 seed = Long.valueOf(System.getProperty("seed")); 45 } catch (NumberFormatException e) { 46 // do nothing: seed is still null 47 } 48 49 return seed; 50 } 51 52 /** 53 * Obtain a seed from an independent PRNG. 54 * 55 * @return A random seed. 56 */ 57 private static long getRandomSeed() { 58 return new Random().nextLong(); 59 } 60 61 /** 62 * Obtain and print to STDOUT a seed appropriate for initializing a PRNG. 63 * If the system property "seed" is set and has value which may be correctly 64 * parsed it is used, otherwise a seed is generated using an independent 65 * PRNG. 66 * 67 * @return The seed. 68 */ 69 public static long getSeed() { 70 Long seed = getSystemSeed(); 71 if (seed == null) { 72 seed = getRandomSeed(); 73 } 74 System.out.println("Seed from RandomFactory = "+seed+"L"); 75 return seed; 76 } 77 78 /** 79 * Obtain and print to STDOUT a seed and use it to initialize a new 80 * {@code Random} instance which is returned. If the system 81 * property "seed" is set and has value which may be correctly parsed it 82 * is used, otherwise a seed is generated using an independent PRNG. 83 * 84 * @return The {@code Random} instance. 85 */ 86 public static Random getRandom() { 87 return new Random(getSeed()); 88 } 89 90 /** 91 * Obtain and print to STDOUT a seed and use it to initialize a new 92 * {@code SplittableRandom} instance which is returned. If the system 93 * property "seed" is set and has value which may be correctly parsed it 94 * is used, otherwise a seed is generated using an independent PRNG. 95 * 96 * @return The {@code SplittableRandom} instance. 97 */ 98 public static SplittableRandom getSplittableRandom() { 99 return new SplittableRandom(getSeed()); 100 } 101 }