简单实现一个java公平策略的锁-优快云博客

本文介绍了一个简单的自定义并发锁的实现方法，通过使用Java的LockSupport工具类来模拟线程间的锁定与解锁行为，并通过一个测试用例验证了其实现的有效性。

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代码是：


package com.eyu.gift.lock;

import java.util.Queue;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.locks.LockSupport;

class FailLock {

	Queue<Thread> queue = new ConcurrentLinkedQueue<Thread>();

	public void lock() {
		queue.add(Thread.currentThread());
		if (queue.peek() != Thread.currentThread()) {
			LockSupport.park(this);
		}
	}

	public void unlock() {
		queue.remove();
		LockSupport.unpark(queue.peek());

	}

}

测试代码：


package com.eyu.gift.lock;

import java.util.concurrent.CountDownLatch;

import org.hamcrest.Matchers;
import org.junit.Assert;
import org.junit.Test;

public class FailLockTest {
	public static final int NUM = 5000;
	public static final int THREAD_NUM = 40;
	static int[] target = new int[THREAD_NUM];

	@Test
	public void test() throws Exception {
		final FailLock failLock = new FailLock();
		final CountDownLatch endCountDownLatch = new CountDownLatch(THREAD_NUM);
		final CountDownLatch startCountDownLatch = new CountDownLatch(1);

		for (int j = 0; j < THREAD_NUM; j++) {
			final int thread = j;
			Thread t = new Thread() {
				@Override
				public void run() {
					try {
						startCountDownLatch.await();
					} catch (InterruptedException e) {
						e.printStackTrace();
					}
					for (int i = 0; i < NUM; i++) {
						failLock.lock();
						++target[thread];
//						System.err.println(target[thread] + "  ========  " + Thread.currentThread().getName());
						failLock.unlock();
					}
					endCountDownLatch.countDown();

				}

			};
			t.setName("线程" + thread);
			t.start();
		}

		startCountDownLatch.countDown();
		endCountDownLatch.await();
		int total = 0;
		for (int i = 0; i < THREAD_NUM; i++) {
			total += target[i];
		}
		Assert.assertThat(total, Matchers.is(THREAD_NUM * NUM));
	}
}