Atomic Pseudo Random : Random « Development Class « Java

Atomic Pseudo Random

 * @(#)$Id$
 * Copyright 2006-2008 Makoto YUI
 * 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
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * Contributors:
 *     Makoto YUI - initial implementation
//package xbird.util.concurrent.lang;

import java.util.concurrent.atomic.AtomicInteger;

 * <DIV lang="en"></DIV>
 * <DIV lang="ja"></DIV>
 * @author Makoto YUI (
public final class AtomicPseudoRandom {

    private final AtomicInteger seed;

    public AtomicPseudoRandom() {
        this((int) System.nanoTime());

    public AtomicPseudoRandom(int seed) {
        this.seed = new AtomicInteger(seed);

    public int nextInt(int n) {
        while(true) {
            int s = seed.get();
            int nextSeed = calculateNext(s);
            if(seed.compareAndSet(s, nextSeed)) {
                int remainder = s % n;
                return remainder > 0 ? remainder : remainder + n;

    private int calculateNext(int s) {
        s ^= s << 6;
        s ^= s >>> 21;
        s ^= (s << 7);
        return s;



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