Mega Code Archive
Random Util with ReentrantLock
<![CDATA[
/*
* @(#)RandomUtil.java 1.0 Apr 26, 2008
*
* The MIT License
*
* Copyright (c) 2008 Malachi de AElfweald <malachid@gmail.com>
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
//package org.eoti.math;
import java.math.BigInteger;
import java.util.Date;
import java.util.Random;
import java.util.concurrent.locks.ReentrantLock;
public class RandomUtil
{
protected static ReentrantLock singletonLock = new ReentrantLock();
protected static RandomUtil singleton;
public static RandomUtil getInstance()
{
// If singleton != null, then just return it (don't lock READ)
if(singleton == null)
{
// don't let more that one person create the singleton
singletonLock.lock();
// if we were waiting for a lock, then someone else already made it
if(singleton == null)
singleton = new RandomUtil();
singletonLock.unlock();
}
return singleton;
}
protected RandomUtil()
{
random = new Random( (new Date()).getTime() );
}
protected Random random;
public static int randInt(int maxNumExclusive)
{
return getInstance().random.nextInt(maxNumExclusive);
}
public static BigInteger randomBitFlip(BigInteger n)
{
if(n.equals(BigInteger.ONE)) return BigInteger.ONE;
if(n.equals(BigInteger.ZERO)) return BigInteger.ZERO;
BigInteger toRet = BigInteger.ONE;
while(toRet.equals(BigInteger.ONE) || toRet.equals(BigInteger.ZERO))
{
byte[] bytes = n.toByteArray();
getInstance().random.nextBytes( bytes );
// could allow up to maxExclusive by converting and checking value
// but this is faster, even if it doesn't give us full range
bytes[0] = 0;
toRet = new BigInteger(bytes);
}
return toRet;
}
}
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