checkState

Checks state preconditions.

Example:

    var result = Preconditions.checkState (isOpen, "resource is closed");
    if (result.isError ()) {
        return;
    }

Parameters:

cond	condition that must be true.
message	error message when condition is false.

Returns:

Result.ok(true) on success, or Result.error(PreconditionError.INVALID_STATE) when condition is false.