如:对一个自定义缓存的测试
//自定义的缓存public class SemaphoreBoundedBuffer <E> {private final Semaphore availableItems, availableSpaces;private final E[] items;private int putPosition = 0, takePosition = 0;public SemaphoreBoundedBuffer(int capacity) {if (capacity <= 0)throw new IllegalArgumentException(); availableItems = new Semaphore(0); availableSpaces = new Semaphore(capacity); items = (E[]) new Object[capacity]; }public boolean isEmpty() {return availableItems.availablePermits() == 0; }public boolean isFull() {return availableSpaces.availablePermits() == 0; }public void put(E x) throws InterruptedException { availableSpaces.acquire(); doInsert(x); availableItems.release(); }public E take() throws InterruptedException { availableItems.acquire(); E item = doExtract(); availableSpaces.release();return item; }private synchronized void doInsert(E x) {int i = putPosition; items[i] = x; putPosition = (++i == items.length) ? 0 : i; }private synchronized E doExtract() {int i = takePosition; E x = items[i]; items[i] = null; takePosition = (++i == items.length) ? 0 : i;return x; } }//无需比较每次 生产者和消费者取出的值;只需要最终比较和即可public class PutTakeTest extends TestCase {protected static final ExecutorService pool = Executors.newCachedThreadPool();protected CyclicBarrier barrier;protected final SemaphoreBoundedBuffer<Integer> bb;protected final int nTrials, nPairs;protected final AtomicInteger putSum = new AtomicInteger(0);protected final AtomicInteger takeSum = new AtomicInteger(0);public static void main(String[] args) throws Exception {new PutTakeTest(10, 10, 100000).test(); // sample parameters pool.shutdown(); }public PutTakeTest(int capacity, int npairs, int ntrials) {this.bb = new SemaphoreBoundedBuffer<Integer>(capacity);this.nTrials = ntrials;this.nPairs = npairs;this.barrier = new CyclicBarrier(npairs * 2 + 1); //初始化为 线程数量*2 + 1:生产者+消费者+主线程 }void test() {try {for (int i = 0; i < nPairs; i++) { pool.execute(new Producer()); pool.execute(new Consumer()); } barrier.await(); // 等待所有线程初始化完成,完成后复位栅栏barrier.await(); // 等待所有线程执行完成assertEquals(putSum.get(), takeSum.get()); //执行比较,判断线程安全性能} catch (Exception e) {throw new RuntimeException(e); } }static int xorShift(int y) { //生成随机数y ^= (y << 6); y ^= (y >>> 21); y ^= (y << 7);return y; }class Producer implements Runnable {public void run() {try {int seed = (this.hashCode() ^ (int) System.nanoTime());int sum = 0; barrier.await(); //等待所有线程初始化完成for (int i = nTrials; i > 0; --i) { bb.put(seed); sum += seed; seed = xorShift(seed); } putSum.getAndAdd(sum); barrier.await(); //等待所有线程执行完成} catch (Exception e) {throw new RuntimeException(e); } } }class Consumer implements Runnable {public void run() {try { barrier.await(); //等待所有线程初始化完成int sum = 0;for (int i = nTrials; i > 0; --i) { sum += bb.take(); } takeSum.getAndAdd(sum); barrier.await(); //等待所有线程执行完成} catch (Exception e) {throw new RuntimeException(e); } } } }
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