001 /* 002 * Licensed to the Apache Software Foundation (ASF) under one 003 * or more contributor license agreements. See the NOTICE file 004 * distributed with this work for additional information 005 * regarding copyright ownership. The ASF licenses this file 006 * to you under the Apache License, Version 2.0 (the 007 * "License"); you may not use this file except in compliance 008 * with the License. You may obtain a copy of the License at 009 * 010 * http://www.apache.org/licenses/LICENSE-2.0 011 * 012 * Unless required by applicable law or agreed to in writing, 013 * software distributed under the License is distributed on an 014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 015 * KIND, either express or implied. See the License for the 016 * specific language governing permissions and limitations 017 * under the License. 018 */ 019 package org.apache.commons.lang.math; 020 021 import java.util.Random; 022 023 /** 024 * <p><code>JVMRandom</code> is a wrapper that supports all possible 025 * Random methods via the {@link java.lang.Math#random()} method 026 * and its system-wide {@link Random} object.</p> 027 * 028 * @since 2.0 029 * @version $Id: JVMRandom.java 471626 2006-11-06 04:02:09Z bayard $ 030 */ 031 public final class JVMRandom extends Random { 032 033 /** 034 * Required for serialization support. 035 * 036 * @see java.io.Serializable 037 */ 038 private static final long serialVersionUID = 1L; 039 040 /** 041 * Ensures that only the constructor can call reseed. 042 */ 043 private boolean constructed = false; 044 045 /** 046 * Constructs a new instance. 047 */ 048 public JVMRandom() { 049 this.constructed = true; 050 } 051 052 /** 053 * Unsupported in 2.0. 054 * 055 * @param seed ignored 056 * @throws UnsupportedOperationException 057 */ 058 public synchronized void setSeed(long seed) { 059 if (this.constructed) { 060 throw new UnsupportedOperationException(); 061 } 062 } 063 064 /** 065 * Unsupported in 2.0. 066 * 067 * @return Nothing, this method always throws an UnsupportedOperationException. 068 * @throws UnsupportedOperationException 069 */ 070 public synchronized double nextGaussian() { 071 throw new UnsupportedOperationException(); 072 } 073 074 /** 075 * Unsupported in 2.0. 076 * 077 * @param byteArray ignored 078 * @throws UnsupportedOperationException 079 */ 080 public void nextBytes(byte[] byteArray) { 081 throw new UnsupportedOperationException(); 082 } 083 084 /** 085 * <p>Returns the next pseudorandom, uniformly distributed int value 086 * from the Math.random() sequence.</p> 087 * 088 * @return the random int 089 */ 090 public int nextInt() { 091 return nextInt(Integer.MAX_VALUE); 092 } 093 /** 094 * <p>Returns a pseudorandom, uniformly distributed int value between 095 * <code>0</code> (inclusive) and the specified value (exclusive), from 096 * the Math.random() sequence.</p> 097 * 098 * @param n the specified exclusive max-value 099 * @return the random int 100 * @throws IllegalArgumentException when <code>n <= 0</code> 101 */ 102 public int nextInt(int n) { 103 if (n <= 0) { 104 throw new IllegalArgumentException( 105 "Upper bound for nextInt must be positive" 106 ); 107 } 108 // TODO: check this cannot return 'n' 109 return (int)(Math.random() * n); 110 } 111 /** 112 * <p>Returns the next pseudorandom, uniformly distributed long value 113 * from the Math.random() sequence.</p> 114 * @return the random long 115 */ 116 public long nextLong() { 117 // possible loss of precision? 118 return nextLong(Long.MAX_VALUE); 119 } 120 121 122 /** 123 * <p>Returns a pseudorandom, uniformly distributed long value between 124 * <code>0</code> (inclusive) and the specified value (exclusive), from 125 * the Math.random() sequence.</p> 126 * 127 * @param n the specified exclusive max-value 128 * @return the random long 129 * @throws IllegalArgumentException when <code>n <= 0</code> 130 */ 131 public static long nextLong(long n) { 132 if (n <= 0) { 133 throw new IllegalArgumentException( 134 "Upper bound for nextInt must be positive" 135 ); 136 } 137 // TODO: check this cannot return 'n' 138 return (long)(Math.random() * n); 139 } 140 141 /** 142 * <p>Returns the next pseudorandom, uniformly distributed boolean value 143 * from the Math.random() sequence.</p> 144 * 145 * @return the random boolean 146 */ 147 public boolean nextBoolean() { 148 return Math.random() > 0.5; 149 } 150 /** 151 * <p>Returns the next pseudorandom, uniformly distributed float value 152 * between <code>0.0</code> and <code>1.0</code> from the Math.random() 153 * sequence.</p> 154 * 155 * @return the random float 156 */ 157 public float nextFloat() { 158 return (float)Math.random(); 159 } 160 /** 161 * <p>Synonymous to the Math.random() call.</p> 162 * 163 * @return the random double 164 */ 165 public double nextDouble() { 166 return Math.random(); 167 } 168 169 }