poll

Immediately answer the value already associated with the specified key. Do not execute the user-supplied transformer under any circumstances. That is, only answer an already cached value.

This method answers null if 1) the cached value associated with the specified key is actually null or 2) no value has been cached for the specified key.

Note that this method is not reentrant. The transformer must not reenter any public operation while computing a value for a specified key.

Return

The value to which the specified key is mapped, or null if no value has been mapped.

Parameters