public void updateValue(double deltaX, double deltaY) {
    long stamp = lock.writeLock();  // 獲取寫鎖
    try {
        x += deltaX;
        y += deltaY;
    } finally {
        lock.unlockWrite(stamp);  // 釋放寫鎖
    }
}

public double readValue() {
    long stamp = lock.readLock();  // 獲取讀鎖
    try {
        return Math.sqrt(x * x + y * y);
    } finally {
        lock.unlockRead(stamp);  // 釋放讀鎖
    }
}

public double readValueOptimistically() {
    long stamp = lock.tryOptimisticRead();  // 獲取樂觀讀鎖
    double currentX = x, currentY = y;

    if (!lock.validate(stamp)) {  // 驗證數(shù)據(jù)是否一致
        stamp = lock.readLock();  // 如果不一致，降級為悲觀讀鎖
        try {
            currentX = x;
            currentY = y;
        } finally {
            lock.unlockRead(stamp);  // 釋放悲觀讀鎖
        }
    }

    return Math.sqrt(currentX * currentX + currentY * currentY);
}

public void conditionalUpdate(double deltaX, double deltaY) {
    long stamp = lock.readLock();  // 獲取悲觀讀鎖
    try {
        if (x == 0 && y == 0) {  // 檢查條件
            stamp = lock.tryConvertToWriteLock(stamp);  // 升級為寫鎖
            if (stamp == 0L) {  // 如果升級失敗
                stamp = lock.writeLock();  // 顯式獲取寫鎖
            }
            x += deltaX;
            y += deltaY;
        }
    } finally {
        lock.unlock(stamp);  // 釋放鎖
    }
}