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RandomData |
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| 1.0;1 |
1 | /* |
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2 | * Copyright 2003-2004 The Apache Software Foundation. |
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3 | * |
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4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
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5 | * you may not use this file except in compliance with the License. |
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6 | * You may obtain a copy of the License at |
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7 | * |
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8 | * http://www.apache.org/licenses/LICENSE-2.0 |
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9 | * |
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10 | * Unless required by applicable law or agreed to in writing, software |
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11 | * distributed under the License is distributed on an "AS IS" BASIS, |
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12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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13 | * See the License for the specific language governing permissions and |
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14 | * limitations under the License. |
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15 | */ |
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16 | ||
17 | package org.apache.commons.math.random; |
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18 | import java.util.Collection; |
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19 | ||
20 | /** |
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21 | * Random data generation utilities |
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22 | * @version $Revision$ $Date: 2005-02-26 05:11:52 -0800 (Sat, 26 Feb 2005) $ |
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23 | */ |
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24 | public interface RandomData { |
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25 | /** |
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26 | * Generates a random string of hex characters of length |
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27 | * <code>len</code>. |
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28 | * <p> |
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29 | * The generated string will be random, but not cryptographically |
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30 | * secure. To generate cryptographically secure strings, use |
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31 | * <code>nextSecureHexString</code> |
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32 | * <p> |
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33 | * <strong>Preconditions</strong>:<ul> |
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34 | * <li><code>len > 0</code> (otherwise an IllegalArgumentException |
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35 | * is thrown.)</li> |
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36 | * </ul> |
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37 | * |
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38 | * @param len the length of the string to be generated |
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39 | * @return random string of hex characters of length <code>len</code> |
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40 | */ |
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41 | String nextHexString(int len); |
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42 | ||
43 | /** |
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44 | * Generates a uniformly distributed random integer between |
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45 | * <code>lower</code> and <code>upper</code> (endpoints included). |
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46 | * <p> |
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47 | * The generated integer will be random, but not cryptographically secure. |
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48 | * To generate cryptographically secure integer sequences, use |
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49 | * <code>nextSecureInt</code>. |
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50 | * <p> |
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51 | * <strong>Preconditions</strong>:<ul> |
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52 | * <li><code>lower < upper</code> (otherwise an IllegalArgumentException |
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53 | * is thrown.)</li> |
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54 | * </ul> |
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55 | * |
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56 | * @param lower lower bound for generated integer |
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57 | * @param upper upper bound for generated integer |
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58 | * @return a random integer greater than or equal to <code>lower</code> |
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59 | * and less than or equal to <code>upper</code>. |
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60 | */ |
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61 | int nextInt(int lower, int upper); |
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62 | ||
63 | /** |
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64 | * Generates a uniformly distributed random long integer between |
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65 | * <code>lower</code> and <code>upper</code> (endpoints included). |
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66 | * <p> |
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67 | * The generated long integer values will be random, but not |
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68 | * cryptographically secure. |
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69 | * To generate cryptographically secure sequences of longs, use |
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70 | * <code>nextSecureLong</code> |
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71 | * <p> |
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72 | * <strong>Preconditions</strong>:<ul> |
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73 | * <li><code>lower < upper</code> (otherwise an IllegalArgumentException |
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74 | * is thrown.)</li> |
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75 | * </ul> |
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76 | * |
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77 | * @param lower lower bound for generated integer |
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78 | * @param upper upper bound for generated integer |
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79 | * @return a random integer greater than or equal to <code>lower</code> |
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80 | * and less than or equal to <code>upper</code>. |
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81 | */ |
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82 | long nextLong(long lower, long upper); |
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83 | ||
84 | /** |
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85 | * Generates a random string of hex characters from a secure random |
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86 | * sequence. |
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87 | * <p> |
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88 | * If cryptographic security is not required, |
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89 | * use <code>nextHexString()</code>. |
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90 | * <p> |
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91 | * <strong>Preconditions</strong>:<ul> |
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92 | * <li><code>len > 0</code> (otherwise an IllegalArgumentException |
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93 | * is thrown.)</li> |
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94 | * </ul> |
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95 | * @param len length of return string |
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96 | * @return the random hex string |
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97 | */ |
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98 | String nextSecureHexString(int len); |
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99 | ||
100 | /** |
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101 | * Generates a uniformly distributed random integer between |
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102 | * <code>lower</code> and <code>upper</code> (endpoints included) |
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103 | * from a secure random sequence. |
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104 | * <p> |
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105 | * Sequences of integers generated using this method will be |
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106 | * cryptographically secure. If cryptographic security is not required, |
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107 | * <code>nextInt</code> should be used instead of this method. |
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108 | * <p> |
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109 | * <strong>Definition</strong>: |
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110 | * <a href="http://en.wikipedia.org/wiki/Cryptographically_secure_pseudo-random_number_generator"> |
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111 | * Secure Random Sequence</a> |
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112 | * <p> |
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113 | * <strong>Preconditions</strong>:<ul> |
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114 | * <li><code>lower < upper</code> (otherwise an IllegalArgumentException |
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115 | * is thrown.)</li> |
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116 | * </ul> |
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117 | * |
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118 | * @param lower lower bound for generated integer |
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119 | * @param upper upper bound for generated integer |
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120 | * @return a random integer greater than or equal to <code>lower</code> |
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121 | * and less than or equal to <code>upper</code>. |
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122 | */ |
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123 | int nextSecureInt(int lower, int upper); |
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124 | ||
125 | /** |
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126 | * Generates a random long integer between <code>lower</code> |
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127 | * and <code>upper</code> (endpoints included).<p> |
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128 | * Sequences of long values generated using this method will be |
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129 | * cryptographically secure. If cryptographic security is not required, |
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130 | * <code>nextLong</code> should be used instead of this method. |
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131 | * <p> |
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132 | * <strong>Definition</strong>: |
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133 | * <a href="http://en.wikipedia.org/wiki/Cryptographically_secure_pseudo-random_number_generator"> |
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134 | * Secure Random Sequence</a> |
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135 | * <p> |
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136 | * <strong>Preconditions</strong>:<ul> |
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137 | * <li><code>lower < upper</code> (otherwise an IllegalArgumentException |
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138 | * is thrown.)</li> |
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139 | * </ul> |
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140 | * |
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141 | * @param lower lower bound for generated integer |
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142 | * @param upper upper bound for generated integer |
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143 | * @return a long integer greater than or equal to <code>lower</code> |
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144 | * and less than or equal to <code>upper</code>. |
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145 | */ |
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146 | long nextSecureLong(long lower, long upper); |
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147 | ||
148 | /** |
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149 | * Generates a random value from the Poisson distribution with |
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150 | * the given mean. |
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151 | * <p> |
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152 | * <strong>Definition</strong>: |
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153 | * <a href="http://www.itl.nist.gov/div898/handbook/eda/section3/eda366j.htm"> |
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154 | * Poisson Distribution</a> |
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155 | * <p> |
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156 | * <strong>Preconditions</strong>: <ul> |
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157 | * <li>The specified mean <i>must</i> be positive (otherwise an |
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158 | * IllegalArgumentException is thrown.)</li> |
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159 | * </ul> |
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160 | * @param mean Mean of the distribution |
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161 | * @return poisson deviate with the specified mean |
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162 | */ |
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163 | long nextPoisson(double mean); |
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164 | ||
165 | /** |
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166 | * Generates a random value from the |
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167 | * Normal (or Gaussian) distribution with the given mean |
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168 | * and standard deviation. |
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169 | * <p> |
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170 | * <strong>Definition</strong>: |
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171 | * <a href="http://www.itl.nist.gov/div898/handbook/eda/section3/eda3661.htm"> |
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172 | * Normal Distribution</a> |
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173 | * <p> |
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174 | * <strong>Preconditions</strong>: <ul> |
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175 | * <li><code>sigma > 0</code> (otherwise an IllegalArgumentException |
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176 | * is thrown.)</li> |
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177 | * </ul> |
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178 | * @param mu Mean of the distribution |
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179 | * @param sigma Standard deviation of the distribution |
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180 | * @return random value from Gaussian distribution with mean = mu, |
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181 | * standard deviation = sigma |
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182 | */ |
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183 | double nextGaussian(double mu, double sigma); |
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184 | ||
185 | /** |
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186 | * Generates a random value from the exponential distribution |
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187 | * with expected value = <code>mean</code>. |
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188 | * <p> |
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189 | * <strong>Definition</strong>: |
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190 | * <a href="http://www.itl.nist.gov/div898/handbook/eda/section3/eda3667.htm"> |
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191 | * Exponential Distribution</a> |
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192 | * <p> |
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193 | * <strong>Preconditions</strong>: <ul> |
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194 | * <li><code>mu >= 0</code> (otherwise an IllegalArgumentException |
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195 | * is thrown.)</li> |
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196 | * </ul> |
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197 | * @param mean Mean of the distribution |
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198 | * @return random value from exponential distribution |
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199 | */ |
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200 | double nextExponential(double mean); |
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201 | ||
202 | /** |
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203 | * Generates a uniformly distributed random value from the open interval |
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204 | * (<code>lower</code>,<code>upper</code>) (i.e., endpoints excluded). |
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205 | * <p> |
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206 | * <strong>Definition</strong>: |
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207 | * <a href="http://www.itl.nist.gov/div898/handbook/eda/section3/eda3662.htm"> |
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208 | * Uniform Distribution</a> <code>lower</code> and |
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209 | * <code>upper - lower</code> are the |
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210 | * <a href = "http://www.itl.nist.gov/div898/handbook/eda/section3/eda364.htm"> |
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211 | * location and scale parameters</a>, respectively. |
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212 | * <p> |
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213 | * <strong>Preconditions</strong>:<ul> |
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214 | * <li><code>lower < upper</code> (otherwise an IllegalArgumentException |
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215 | * is thrown.)</li> |
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216 | * </ul> |
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217 | * |
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218 | * @param lower lower endpoint of the interval of support |
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219 | * @param upper upper endpoint of the interval of support |
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220 | * @return uniformly distributed random value between lower |
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221 | * and upper (exclusive) |
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222 | */ |
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223 | double nextUniform(double lower, double upper); |
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224 | ||
225 | /** |
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226 | * Generates an integer array of length <code>k</code> whose entries |
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227 | * are selected randomly, without repetition, from the integers <code> |
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228 | * 0 through n-1</code> (inclusive). |
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229 | * <p> |
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230 | * Generated arrays represent permutations |
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231 | * of <code>n</code> taken <code>k</code> at a time. |
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232 | * <p> |
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233 | * <strong>Preconditions:</strong><ul> |
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234 | * <li> <code>k <= n</code></li> |
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235 | * <li> <code>n > 0</code> </li> |
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236 | * </ul> |
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237 | * If the preconditions are not met, an IllegalArgumentException is |
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238 | * thrown. |
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239 | * |
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240 | * @param n domain of the permutation |
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241 | * @param k size of the permutation |
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242 | * @return random k-permutation of n |
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243 | */ |
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244 | int[] nextPermutation(int n, int k); |
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245 | ||
246 | /** |
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247 | * Returns an array of <code>k</code> objects selected randomly |
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248 | * from the Collection <code>c</code>. |
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249 | * <p> |
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250 | * Sampling from <code>c</code> |
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251 | * is without replacement; but if <code>c</code> contains identical |
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252 | * objects, the sample may include repeats. If all elements of <code> |
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253 | * c</code> are distinct, the resulting object array represents a |
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254 | * <a href="http://rkb.home.cern.ch/rkb/AN16pp/node250.html#SECTION0002500000000000000000"> |
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255 | * Simple Random Sample</a> of size |
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256 | * <code>k</code> from the elements of <code>c</code>. |
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257 | * <p> |
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258 | * <strong>Preconditions:</strong><ul> |
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259 | * <li> k must be less than or equal to the size of c </li> |
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260 | * <li> c must not be empty </li> |
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261 | * </ul> |
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262 | * If the preconditions are not met, an IllegalArgumentException is |
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263 | * thrown. |
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264 | * |
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265 | * @param c collection to be sampled |
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266 | * @param k size of the sample |
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267 | * @return random sample of k elements from c |
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268 | */ |
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269 | Object[] nextSample(Collection c, int k); |
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270 | } |