併發程式測試

 一、正確性測試

　　如：對一個自定義緩存的測試

//自定義的緩存
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;
    }
}

//無需比較每次 生產者和消費者取出的值；只需要最終比較和即可
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);   //初始化為 線程數量*2 + 1：生產者+消費者+主線程
    }
    void test() {
        try {
            for (int i = 0; i < nPairs; i++) {
                pool.execute(new Producer());
                pool.execute(new Consumer());
            }
            barrier.await(); // 等待所有線程初始化完成，完成後複位柵欄
            barrier.await(); // 等待所有線程執行完成
            assertEquals(putSum.get(), takeSum.get());      //執行比較，判斷線程安全性能
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
    static int xorShift(int y) {    //生成隨機數
        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();                        //等待所有線程初始化完成
                for (int i = nTrials; i > 0; --i) {
                    bb.put(seed);
                    sum += seed;
                    seed = xorShift(seed);
                }
                putSum.getAndAdd(sum);
                barrier.await();                        //等待所有線程執行完成
            } catch (Exception e) {
                throw new RuntimeException(e);
            }
        }
    }
    class Consumer implements Runnable {
        public void run() {
            try {
                barrier.await();                        //等待所有線程初始化完成
                int sum = 0;
                for (int i = nTrials; i > 0; --i) {
                    sum += bb.take();
                }
                takeSum.getAndAdd(sum);
                barrier.await();                        //等待所有線程執行完成
            } catch (Exception e) {
                throw new RuntimeException(e);
            }
        }
    }
}