CharStream A source of characters for an ANTLR lexer
 IntStream A simple stream of integers used when all I care about is the char or token type sequence (such as interpretation).
 TokenSource A source of tokens must provide a sequence of tokens via nextToken() and also must reveal it's source of characters; CommonToken's text is computed from a CharStream; it only store indices into the char stream.
 TokenStream A stream of tokens accessing tokens from a TokenSource
 BaseRecognizer A generic recognizer that can handle recognizers generated from lexer, parser, and tree grammars.
 BitSetA stripped-down version of org.antlr.misc.BitSet that is just good enough to handle runtime requirements such as FOLLOW sets for automatic error recovery.
 CharStreamState When walking ahead with cyclic DFA or for syntactic predicates, we need to record the state of the input stream (char index, line, etc...) so that we can rewind the state after scanning ahead.
 CommonTokenStream The most common stream of tokens is one where every token is buffered up and tokens are prefiltered for a certain channel (the parser will only see these tokens and cannot change the filter channel number during the parse).
 DFA A DFA implemented as a set of transition tables.
 EarlyExitException The recognizer did not match anything for a (..)+ loop.
 FailedPredicateException A semantic predicate failed during validation.
 Lexer A lexer is recognizer that draws input symbols from a character stream.
 MismatchedTokenException A mismatched char or Token or tree node
 Parser A parser for TokenStreams.
 ParserRuleReturnScope Rules that return more than a single value must return an object containing all the values.
 RecognitionException The root of the ANTLR exception hierarchy.
 RecognizerSharedState The set of fields needed by an abstract recognizer to recognize input and recover from errors etc...
 RuleReturnScope Rules can return start/stop info as well as possible trees and templates
 TokenRewriteStream Useful for dumping out the input stream after doing some augmentation or other manipulations.