protected int getLexerActionIndex(LexerAction lexerAction) {
		Integer lexerActionIndex = actionToIndexMap.get(lexerAction);
		if (lexerActionIndex == null) {
			lexerActionIndex = actionToIndexMap.size();
			actionToIndexMap.put(lexerAction, lexerActionIndex);
			indexToActionMap.put(lexerActionIndex, lexerAction);
		}

		return lexerActionIndex;
	}
Maps from a {@link LexerAction} object to the action index.
tool/src/org/antlr/v4/automata/LexerATNFactory.java