我面临着一个关于

StampedLock的奇怪行为.以下是主要有问题的代码行：

StampedLock lock = new StampedLock();

long stamp1 = lock.readLock();

System.out.printf("Read lock count: %d%n", lock.getReadLockCount());

lock.unlock(stamp1 + 2);

System.out.printf("Read lock count: %d%n", lock.getReadLockCount());

奇怪的行为是关于如何解锁“容忍”错误的读取标记.你觉得这样对吗？

这里是参考的完整代码：

public class StampedLockExample {

static StampedLock lock = new StampedLock();

static void println(String message, Object... args) {

System.out.printf(message, args);

System.out.println();

}

static void printReadLockCount() {

println("Lock count=%d", lock.getReadLockCount());

}

static long tryReadLock() {

long stamp = lock.tryReadLock();

println("Gets read lock (%d)", stamp);

printReadLockCount();

return stamp;

}

static long tryWriteLock() {

long stamp = lock.tryWriteLock();

println("Gets write lock (%d)", stamp);

return stamp;

}

static long tryConvertToReadLock(long stamp) {

long newOne = lock.tryConvertToReadLock(stamp);

println("Gets read lock (%d -> %d)", stamp, newOne);

printReadLockCount();

return newOne;

}

static void tryUnlock(long stamp) {

try {

lock.unlock(stamp);

println("Unlock (%d) successfully", stamp);

} catch (IllegalMonitorStateException e) {

println("Unlock (%d) failed", stamp);

}

printReadLockCount();

}

public static void main(String[] args) {

println("%n--- Gets two read locks ---");

long stamp1 = tryReadLock();

long stamp2 = tryReadLock();

long min = Math.min(stamp1, stamp2);

long max = Math.max(stamp1, stamp2);

println("%n--- Tries unlock (-1 / +2 / +4) ---");

tryUnlock(min - 1);

tryUnlock(max + 2);

tryUnlock(max + 4);

println("%n--- Gets write lock ---");

long stamp3 = tryWriteLock();

println("%n--- Tries unlock (-1 / +1) ---");

tryUnlock(stamp3 - 1);

tryUnlock(stamp3 + 1);

println("%n--- Tries write > read conversion ---");

long stamp4 = tryConvertToReadLock(stamp3);

println("%n--- Tries unlock last write stamp (-1 / 0 / +1) ---");

tryUnlock(stamp3 - 1);

tryUnlock(stamp3);

tryUnlock(stamp3 + 1);

println("%n--- Tries unlock (-1 / +1) ---");

tryUnlock(stamp4 - 1);

tryUnlock(stamp4 + 1);

}

}

输出：

--- Gets two read locks ---

Gets read lock (257)

Lock count=1

Gets read lock (258)

Lock count=2

--- Tries unlock (-1 / +2 / +4) ---

Unlock (256) failed

Lock count=2

Unlock (260) successfully

Lock count=1

Unlock (262) successfully

Lock count=0

--- Gets write lock ---

Gets write lock (384)

--- Tries unlock (-1 / +1) ---

Unlock (383) failed

Lock count=0

Unlock (385) failed

Lock count=0

--- Tries write > read conversion ---

Gets read lock (384 -> 513)

Lock count=1

--- Tries unlock last write stamp (-1 / 0 / +1) ---

Unlock (383) failed

Lock count=1

Unlock (384) failed

Lock count=1

Unlock (385) failed

Lock count=1

--- Tries unlock (-1 / +1) ---

Unlock (512) failed

Lock count=1

Unlock (514) successfully

Lock count=0