贴一段代码，一个id的生成器，求解

0 0

贴一段代码，一个id的生成器，求解5

/*
 * This file is part of aion-unique <aion-unique.org>.
 *
 *  aion-unique is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  aion-unique is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with aion-unique.  If not, see <http://www.gnu.org/licenses/>.
 */
package com.aionemu.chatserver.utils;

import java.util.BitSet;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.locks.ReentrantLock;

/**
 * Simplified version of idfactory
 * 
 * @author ATracer
 */
public class IdFactory
{
	private final BitSet		idList		= new BitSet();
	private final ReentrantLock	lock		= new ReentrantLock();
	private AtomicInteger		nextMinId	= new AtomicInteger(1);

	protected static IdFactory	instance	= new IdFactory();

	public int nextId()
	{
		try
		{
			lock.lock();
			int id = idList.nextClearBit(nextMinId.intValue());
			idList.set(id);
			nextMinId.incrementAndGet();
			return id;
		}
		finally
		{
			lock.unlock();
		}
	}

	public static IdFactory getInstance()
	{
		return instance;
	}

	public static void main(String[] xiaoe)
	{
		BitSet idList = new BitSet();
		for (int i = 0; i < 100; i++)
			System.out.println(idList.nextClearBit(i));
	}

}

我觉得有两个问题：
1. 这里既然已经用锁同步了，就可以不用atomic类
2. BitSet有点画蛇添足的味道

不知道作者为何要这么设计，求解。谁能指点下这么写的好处。

bitset

2012年7月02日 17:28

冲杯茶喝
1
0 0 5

3个答案按时间排序按投票排序

0 0

采纳的答案

public class IdFactory {
	private final ReentrantLock lock = new ReentrantLock();
	private volatile int id = 0;
	private static final IdFactory instance = new IdFactory();

	private IdFactory() {
	}

	public int nextId() {
		try {
			lock.lock();
			id++;
			return id;
		} finally {
			lock.unlock();
		}
	}

	public static IdFactory getInstance() {
		return instance;
	}

	static class TestThread extends Thread {
		ArrayList<Integer> idList = new ArrayList<Integer>();

		public void run() {
			IdFactory fac = IdFactory.getInstance();
			for (int i = 0; i < 10000; i++) {
				idList.add(fac.nextId());
			}
		}
	}

	public static void main(String[] arg) throws Exception {
		TestThread t1 = new TestThread();
		TestThread t2 = new TestThread();
		t1.start();
		t2.start();
		t1.join();
		t2.join();
		System.out.println(t1.idList.size());
		System.out.println(t2.idList.size());
		t1.idList.removeAll(t2.idList);
		System.out.println(t1.idList.size());
		System.out.println(t2.idList.size());
	}
}

我这样写，效果应该一样吧！

2012年7月03日 08:44