randomgenerator.java

Apache的common math数学软件包

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.math.random;

import java.io.Serializable;

/**
 * Interface extracted from <code>java.util.Random</code>.  This interface is
 * implemented by {@link AbstractRandomGenerator}.  
 *
 * @since 1.1
 * @version $Revision: 628614 $ $Date: 2008-02-17 21:47:53 -0700 (Sun, 17 Feb 2008) $
 */
public interface RandomGenerator extends Serializable {
    
    /**
     * Sets the seed of the underyling random number generator using a 
     * <code>long</code> seed.  Sequences of values generated starting with the
     * same seeds should be identical.
     *
     * @param seed the seed value
     */
    void setSeed(long seed);
    
    /**
     * Generates random bytes and places them into a user-supplied 
     * byte array.  The number of random bytes produced is equal to 
     * the length of the byte array.
     * 
     * @param bytes the non-null byte array in which to put the 
     * random bytes
     */
    void nextBytes(byte[] bytes);
    
    /**
     * Returns the next pseudorandom, uniformly distributed <code>int</code>
     * value from this random number generator's sequence.  
     * All 2<font size="-1"><sup>32</sup></font> possible <tt>int</tt> values
     * should be produced with  (approximately) equal probability. 
     *
     * @return the next pseudorandom, uniformly distributed <code>int</code>
     *  value from this random number generator's sequence
     */
    int nextInt();
    
    /**
     * Returns a pseudorandom, uniformly distributed <tt>int</tt> value
     * between 0 (inclusive) and the specified value (exclusive), drawn from
     * this random number generator's sequence.   
     *
     * @param n the bound on the random number to be returned.  Must be
     * positive.
     * @return  a pseudorandom, uniformly distributed <tt>int</tt>
     * value between 0 (inclusive) and n (exclusive).
     * @throws IllegalArgumentException  if n is not positive.
     */
    int nextInt(int n);
    
    /**
     * Returns the next pseudorandom, uniformly distributed <code>long</code>
     * value from this random number generator's sequence.  All 
     * 2<font size="-1"><sup>64</sup></font> possible <tt>long</tt> values 
     * should be produced with (approximately) equal probability. 
     *
     * @return  the next pseudorandom, uniformly distributed <code>long</code>
     *value from this random number generator's sequence
     */
    long nextLong();
    
    /**
     * Returns the next pseudorandom, uniformly distributed
     * <code>boolean</code> value from this random number generator's
     * sequence.  
     * 
     * @return  the next pseudorandom, uniformly distributed
     * <code>boolean</code> value from this random number generator's
     * sequence
     */
    boolean nextBoolean();
    
    /**
     * Returns the next pseudorandom, uniformly distributed <code>float</code>
     * value between <code>0.0</code> and <code>1.0</code> from this random
     * number generator's sequence.  
     *
     * @return  the next pseudorandom, uniformly distributed <code>float</code>
     * value between <code>0.0</code> and <code>1.0</code> from this
     * random number generator's sequence
     */
    float nextFloat();
    
    /**
     * Returns the next pseudorandom, uniformly distributed 
     * <code>double</code> value between <code>0.0</code> and
     * <code>1.0</code> from this random number generator's sequence.  
     *
     * @return  the next pseudorandom, uniformly distributed 
     *  <code>double</code> value between <code>0.0</code> and
     *  <code>1.0</code> from this random number generator's sequence
     */  
    double nextDouble();
    
    /**
     * Returns the next pseudorandom, Gaussian ("normally") distributed
     * <code>double</code> value with mean <code>0.0</code> and standard
     * deviation <code>1.0</code> from this random number generator's sequence.
     * 
     * @return  the next pseudorandom, Gaussian ("normally") distributed
     * <code>double</code> value with mean <code>0.0</code> and
     * standard deviation <code>1.0</code> from this random number
     *  generator's sequence
     */
    double nextGaussian();
}