对人生命最大的威胁是以车代步，而不是交通事故。——怀特
对应的单元测试：
代码语言：javascript复制import org.junit.jupiter.api.Test;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicReference;
import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertTrue;
class AtomicReferenceTest {
@Test
void testGetSetPlain() throws InterruptedException {
AtomicReference<String> ref = new AtomicReference<>("initial");
int numberOfThreads = 10;
ExecutorService executor = Executors.newFixedThreadPool(numberOfThreads);
for (int i = 0; i < numberOfThreads; i ) {
executor.submit(() -> ref.setPlain("new"));
}
executor.shutdown();
assertTrue(executor.awaitTermination(1, TimeUnit.MINUTES));
assertEquals("new", ref.getPlain());
}
@Test
void testGetSetAcquireRelease() throws InterruptedException {
AtomicReference<String> ref = new AtomicReference<>("initial");
int numberOfThreads = 10;
ExecutorService executor = Executors.newFixedThreadPool(numberOfThreads);
for (int i = 0; i < numberOfThreads; i ) {
executor.submit(() -> ref.setRelease("new"));
}
executor.shutdown();
assertTrue(executor.awaitTermination(1, TimeUnit.MINUTES));
assertEquals("new", ref.getAcquire());
}
@Test
void testGetSetOpaque() throws InterruptedException {
AtomicReference<String> ref = new AtomicReference<>("initial");
int numberOfThreads = 10;
ExecutorService executor = Executors.newFixedThreadPool(numberOfThreads);
for (int i = 0; i < numberOfThreads; i ) {
executor.submit(() -> ref.setOpaque("new"));
}
executor.shutdown();
assertTrue(executor.awaitTermination(1, TimeUnit.MINUTES));
assertEquals("new", ref.getOpaque());
}
@Test
void testCompareAndExchange() throws InterruptedException {
AtomicReference<String> ref = new AtomicReference<>("initial");
int numberOfThreads = 10;
ExecutorService executor = Executors.newFixedThreadPool(numberOfThreads);
for (int i = 0; i < numberOfThreads; i ) {
executor.submit(() -> ref.compareAndExchange("initial", "changed"));
}
executor.shutdown();
assertTrue(executor.awaitTermination(1, TimeUnit.MINUTES));
assertEquals("changed", ref.get());
}
@Test
void testCompareAndExchangeAcquireRelease() throws InterruptedException {
AtomicReference<String> ref = new AtomicReference<>("initial");
ExecutorService executor = Executors.newSingleThreadExecutor();
executor.submit(() -> assertEquals("initial", ref.compareAndExchangeAcquire("initial", "changed")));
executor.submit(() -> assertEquals("changed", ref.get()));
executor.submit(() -> assertEquals("changed", ref.compareAndExchangeRelease("changed", "new")));
executor.submit(() -> assertEquals("new", ref.get()));
executor.shutdown();
assertTrue(executor.awaitTermination(1, TimeUnit.MINUTES));
}
@Test
void testWeakCompareAndSetVolatile() throws InterruptedException {
AtomicReference<String> ref = new AtomicReference<>("initial");
int numberOfThreads = 10;
ExecutorService executor = Executors.newFixedThreadPool(numberOfThreads);
for (int i = 0; i < numberOfThreads; i ) {
executor.submit(() -> assertTrue(ref.weakCompareAndSetVolatile("initial", "changed")));
}
executor.shutdown();
assertTrue(executor.awaitTermination(1, TimeUnit.MINUTES));
assertEquals("changed", ref.get());
}
@Test
void testWeakCompareAndSetAcquireRelease() throws InterruptedException {
AtomicReference<String> ref = new AtomicReference<>("initial");
ExecutorService executor = Executors.newSingleThreadExecutor();
executor.submit(() -> assertTrue(ref.weakCompareAndSetAcquire("initial", "changed")));
executor.submit(() -> assertEquals("changed", ref.get()));
executor.submit(() -> assertTrue(ref.weakCompareAndSetRelease("changed", "new")));
executor.submit(() -> assertEquals("new", ref.get()));
executor.shutdown();
assertTrue(executor.awaitTermination(1, TimeUnit.MINUTES));
}
@Test
void testGetAndSet() throws InterruptedException {
AtomicReference<String> ref = new AtomicReference<>("initial");
int numberOfThreads = 10;
ExecutorService executor = Executors.newFixedThreadPool(numberOfThreads);
for (int i = 0; i < numberOfThreads; i ) {
executor.submit(() -> assertEquals("initial", ref.getAndSet("new")));
}
executor.shutdown();
assertTrue(executor.awaitTermination(1, TimeUnit.MINUTES));
assertEquals("new", ref.get());
}
@Test
void testGetAndUpdate() throws InterruptedException {
AtomicReference<Integer> ref = new AtomicReference<>(0);
int numberOfThreads = 10;
ExecutorService executor = Executors.newFixedThreadPool(numberOfThreads);
for (int i = 0; i < numberOfThreads; i ) {
executor.submit(() -> ref.getAndUpdate(x -> x 1));
}
executor.shutdown();
assertTrue(executor.awaitTermination(1, TimeUnit.MINUTES));
assertEquals(numberOfThreads, ref.get());
}
@Test
void testUpdateAndGet() throws InterruptedException {
AtomicReference<Integer> ref = new AtomicReference<>(0);
int numberOfThreads = 10;
ExecutorService executor = Executors.newFixedThreadPool(numberOfThreads);
for (int i = 0; i < numberOfThreads; i ) {
executor.submit(() -> ref.updateAndGet(x -> x 1));
}
executor.shutdown();
assertTrue(executor.awaitTermination(1, TimeUnit.MINUTES));
assertEquals(numberOfThreads, ref.get());
}
@Test
void testGetAndAccumulate() throws InterruptedException {
AtomicReference<Integer> ref = new AtomicReference<>(0);
int numberOfThreads = 10;
ExecutorService executor = Executors.newFixedThreadPool(numberOfThreads);
for (int i = 0; i < numberOfThreads; i ) {
executor.submit(() -> ref.getAndAccumulate(1, Integer::sum));
}
executor.shutdown();
assertTrue(executor.awaitTermination(1, TimeUnit.MINUTES));
assertEquals(numberOfThreads, ref.get());
}
@Test
void testAccumulateAndGet() throws InterruptedException {
AtomicReference<Integer> ref = new AtomicReference<>(0);
int numberOfThreads = 10;
ExecutorService executor = Executors.newFixedThreadPool(numberOfThreads);
for (int i = 0; i < numberOfThreads; i ) {
executor.submit(() -> ref.accumulateAndGet(1, Integer::sum));
}
executor.shutdown();
assertTrue(executor.awaitTermination(1, TimeUnit.MINUTES));
assertEquals(numberOfThreads, ref.get());
}
@Test
void compareSetAndGetPlainWithVolatile() throws InterruptedException {
AtomicReference<String> ref = new AtomicReference<>("initial");
// set/get (volatile access)
ExecutorService executorVolatile = Executors.newFixedThreadPool(2);
executorVolatile.execute(() -> ref.set("volatileUpdate"));
executorVolatile.execute(() -> assertEquals("volatileUpdate", ref.get()));
executorVolatile.shutdown();
// setPlain/getPlain (non-volatile access)
AtomicReference<String> refPlain = new AtomicReference<>("initial");
ExecutorService executorPlain = Executors.newFixedThreadPool(2);
executorPlain.execute(() -> refPlain.setPlain("plainUpdate"));
executorPlain.execute(() -> assertEquals("plainUpdate", refPlain.getPlain()));
executorPlain.shutdown();
assertTrue(executorVolatile.awaitTermination(1, TimeUnit.SECONDS));
assertTrue(executorPlain.awaitTermination(1, TimeUnit.SECONDS));
}
@Test
void compareCompareAndSetWithWeakCompareAndSetVolatile() throws InterruptedException {
AtomicReference<Integer> ref = new AtomicReference<>(0);
// compareAndSet
ExecutorService executorCAS = Executors.newFixedThreadPool(10);
for (int i = 0; i < 10; i ) {
executorCAS.submit(() -> {
while (!ref.compareAndSet(ref.get(), ref.get() 1)) {
// retry
}
});
}
// weakCompareAndSetVolatile
AtomicReference<Integer> refWeak = new AtomicReference<>(0);
ExecutorService executorWeakCAS = Executors.newFixedThreadPool(10);
for (int i = 0; i < 10; i ) {
executorWeakCAS.submit(() -> {
while (!refWeak.weakCompareAndSetVolatile(refWeak.get(), refWeak.get() 1)) {
// retry
}
});
}
executorCAS.shutdown();
executorWeakCAS.shutdown();
assertTrue(executorCAS.awaitTermination(1, TimeUnit.SECONDS));
assertTrue(executorWeakCAS.awaitTermination(1, TimeUnit.SECONDS));
assertEquals(10, ref.get());
assertEquals(10, refWeak.get());
}
@Test
void compareGetAndSetWithCompareAndExchange() throws InterruptedException {
AtomicReference<String> ref = new AtomicReference<>("initial");
// getAndSet
ExecutorService executorGetAndSet = Executors.newSingleThreadExecutor();
executorGetAndSet.submit(() -> assertEquals("initial", ref.getAndSet("new")));
executorGetAndSet.shutdown();
// compareAndExchange
AtomicReference<String> refExchange = new AtomicReference<>("initial");
ExecutorService executorExchange = Executors.newSingleThreadExecutor();
executorExchange.submit(() -> assertEquals("initial", refExchange.compareAndExchange("initial", "new")));
executorExchange.shutdown();
assertTrue(executorGetAndSet.awaitTermination(1, TimeUnit.SECONDS));
assertTrue(executorExchange.awaitTermination(1, TimeUnit.SECONDS));
assertEquals("new", ref.get());
assertEquals("new", refExchange.get());
}
}
