AtomicInteger使用及性能测试

private AtomicInteger counter = new AtomicInteger(Integer.MAX_VALUE-10);
private final int loop = 20;
private final int concurrency = 1;

@Test
public synchronized void performance() throws InterruptedException {
final int[][] results = new int[concurrency][];
Thread[] threads = new Thread[concurrency];

for (int i = 0; i < concurrency; i++) {
final int[] result = new int[loop];
results[i] = result;
threads[i] = new Thread(new Runnable() {
public void run() {
for (int i = 0; i < loop; i++) {
result[i] = counter.getAndIncrement();
}
}
}, "t-" + (i + 1));
}

long start = System.currentTimeMillis();

for (Thread thread : threads) {
thread.start();
}

for (Thread thread : threads) {
thread.join();
}

long duration = System.currentTimeMillis() - start;

System.out.printf(" requests=%d, concurrency=%d%n", concurrency * loop,
concurrency);

System.out.printf(" Total time: %,d ms.%n", duration);
System.out.printf("Average time: %,2.2f \u03BCs.%n", (double) duration / concurrency / loop * 1000);

// 检查重复
Set<Integer> allIDs = new HashSet();

for (int[] result : results) {
for (int id : result) {
assertNotNull(id);
allIDs.add(id);
}
}

assertEquals(concurrency * loop, allIDs.size());
}