from threading import Lock

class AtomicBoolean:
    '''
    A {@code boolean} value that may be updated atomically. 
    '''
    def __init__(self, val:bool):
        '''
        @param val the initial value
        '''
        self._val = val
        self._lock = Lock()
        
    def get(self):
        '''
        @return the current value
        '''
        return self._val
    
    def compareAndSet(self, expectedValue:bool, newValue:bool)->bool:
        '''
        Atomically sets the value to {@code newValue}
        if the current value {@code == expectedValue}, else do nothing,
        @param expectedValue the expected value
        @param newValue the new value
        @return {@code True} if successful. False return indicates that
        the actual value was not equal to the expected value.
        '''
        with self._lock:
            if not self._val == expectedValue:
                return False
            self._val = newValue
            return True