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Commons.Lang, a package of Java utility classes for the classes that are in java.lang's hierarchy, or are considered to be so standard as to justify existence in java.lang.
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/*
 * Copyright 2002,2004 The Apache Software Foundation.
 * 
 * Licensed 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.lang.math;

import java.util.Random;

/**
 * RandomUtils is a wrapper that supports all possible 
 * {@link java.util.Random} methods via the {@link java.lang.Math#random()}
 * method and its system-wide Random object.
 * 
 * @author Henri Yandell
 * @author Gary D. Gregory
 * @since 2.0
 * @version $Id: RandomUtils.java 155423 2005-02-26 13:08:30Z dirkv $
 */
public class RandomUtils {

    /**
     * An instance of {@link JVMRandom}.
     */
    public static final Random JVM_RANDOM = new JVMRandom();

// should be possible for JVM_RANDOM?
//    public static void nextBytes(byte[]) {
//    public synchronized double nextGaussian();
//    }

    /**
     * 
Returns the next pseudorandom, uniformly distributed int value
     * from the Math.random() sequence.
     *
     * @return the random int
     */
    public static int nextInt() {
        return nextInt(JVM_RANDOM);
    }
    
    /**
     * Returns the next pseudorandom, uniformly distributed int value
     * from the given random sequence.
     *
     * @param random the Random sequence generator.
     * @return the random int
     */
    public static int nextInt(Random random) {
        return random.nextInt();
    }
    
    /**
     * Returns a pseudorandom, uniformly distributed int value
     * between 0 (inclusive) and the specified value
     * (exclusive), from the Math.random() sequence.
     *
     * @param n  the specified exclusive max-value
     * @return the random int
     */
    public static int nextInt(int n) {
        return nextInt(JVM_RANDOM, n);
    }
    
    /**
     * Returns a pseudorandom, uniformly distributed int value
     * between 0 (inclusive) and the specified value
     * (exclusive), from the given Random sequence.
     *
     * @param random the Random sequence generator.
     * @param n  the specified exclusive max-value
     * @return the random int
     */
    public static int nextInt(Random random, int n) {
        // check this cannot return 'n'
        return random.nextInt(n);
    }
    
    /**
     * Returns the next pseudorandom, uniformly distributed long value
     * from the Math.random() sequence.
     *
     * @return the random long
     */
    public static long nextLong() {
        return nextLong(JVM_RANDOM);
    }

    /**
     * Returns the next pseudorandom, uniformly distributed long value
     * from the given Random sequence.
     *
     * @param random the Random sequence generator.
     * @return the random long
     */
    public static long nextLong(Random random) {
        return random.nextLong();
    }
    
    /**
     * Returns the next pseudorandom, uniformly distributed boolean value
     * from the Math.random() sequence.
     *
     * @return the random boolean
     */
    public static boolean nextBoolean() {
        return nextBoolean(JVM_RANDOM);
    }

    /**
     * Returns the next pseudorandom, uniformly distributed boolean value
     * from the given random sequence.
     *
     * @param random the Random sequence generator.
     * @return the random boolean
     */
    public static boolean nextBoolean(Random random) {
        return random.nextBoolean();
    }
    
    /**
     * Returns the next pseudorandom, uniformly distributed float value
     * between 0.0 and 1.0 from the Math.random()
     * sequence.
     *
     * @return the random float
     */
    public static float nextFloat() {
        return nextFloat(JVM_RANDOM);
    }

    /**
     * Returns the next pseudorandom, uniformly distributed float value
     * between 0.0 and 1.0 from the given Random
     * sequence.
     *
     * @param random the Random sequence generator.
     * @return the random float
     */
    public static float nextFloat(Random random) {
        return random.nextFloat();
    }
    
    /**
     * Returns the next pseudorandom, uniformly distributed float value
     * between 0.0 and 1.0 from the Math.random()
     * sequence.
     *
     * @return the random double
     */
    public static double nextDouble() {
        return nextDouble(JVM_RANDOM);
    }

    /**
     * Returns the next pseudorandom, uniformly distributed float value
     * between 0.0 and 1.0 from the given Random
     * sequence.
     *
     * @param random the Random sequence generator.
     * @return the random double
     */
    public static double nextDouble(Random random) {
        return random.nextDouble();
    }
    
}