Allowed derived classes to modify the behavior of operations which change the current stream position by adjusting the target token index of a seek operation.
Allowed derived classes to modify the behavior of operations which change the current stream position by adjusting the target token index of a seek operation. The default implementation simply returns i . If an exception is thrown in this method, the current stream index should not be changed.
For example, CommonTokenStream overrides this method to ensure that the seek target is always an on-channel token.
