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A Java's Collaborative Filtering library to carry out experiments in research of Collaborative Filtering based Recommender Systems. The library has been designed from researchers to researchers.
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/*
 * 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.math3.random;


/**
 * Interface extracted from java.util.Random.  This interface is
 * implemented by {@link AbstractRandomGenerator}.
 *
 * @since 1.1
 */
public interface RandomGenerator {

    /**
     * Sets the seed of the underlying random number generator using an
     * int seed.
     * Sequences of values generated starting with the same seeds
     * should be identical.
     * 
     * @param seed the seed value
     */
    void setSeed(int seed);

    /**
     * Sets the seed of the underlying random number generator using an
     * int array seed.
     * Sequences of values generated starting with the same seeds
     * should be identical.
     * 
     * @param seed the seed value
     */
    void setSeed(int[] seed);

    /**
     * Sets the seed of the underlying random number generator using a
     * long 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 int
     * value from this random number generator's sequence.
     * All 2³² possible {@code int} values
     * should be produced with  (approximately) equal probability.
     *
     * @return the next pseudorandom, uniformly distributed int
     *  value from this random number generator's sequence
     */
    int nextInt();

    /**
     * Returns a pseudorandom, uniformly distributed {@code int} 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 {@code int}
     * value between 0 (inclusive) and n (exclusive).
     * @throws IllegalArgumentException  if n is not positive.
     */
    int nextInt(int n);

    /**
     * Returns the next pseudorandom, uniformly distributed long
     * value from this random number generator's sequence.  All
     * 2⁶⁴ possible {@code long} values
     * should be produced with (approximately) equal probability.
     *
     * @return  the next pseudorandom, uniformly distributed long
     *value from this random number generator's sequence
     */
    long nextLong();

    /**
     * Returns the next pseudorandom, uniformly distributed
     * boolean value from this random number generator's
     * sequence.
     *
     * @return  the next pseudorandom, uniformly distributed
     * boolean value from this random number generator's
     * sequence
     */
    boolean nextBoolean();

    /**
     * Returns the next pseudorandom, uniformly distributed float
     * value between 0.0 and 1.0 from this random
     * number generator's sequence.
     *
     * @return  the next pseudorandom, uniformly distributed float
     * value between 0.0 and 1.0 from this
     * random number generator's sequence
     */
    float nextFloat();

    /**
     * Returns the next pseudorandom, uniformly distributed
     * double value between 0.0 and
     * 1.0 from this random number generator's sequence.
     *
     * @return  the next pseudorandom, uniformly distributed
     *  double value between 0.0 and
     *  1.0 from this random number generator's sequence
     */
    double nextDouble();

    /**
     * Returns the next pseudorandom, Gaussian ("normally") distributed
     * double value with mean 0.0 and standard
     * deviation 1.0 from this random number generator's sequence.
     *
     * @return  the next pseudorandom, Gaussian ("normally") distributed
     * double value with mean 0.0 and
     * standard deviation 1.0 from this random number
     *  generator's sequence
     */
    double nextGaussian();
}