public boolean isValidDecimal() {
	    int nextChar = _input.LA(1);
	    if (nextChar >= 'A' && nextChar <= 'Z' || nextChar >= '0' && nextChar <= '9' ||
	      nextChar == '_') {
	      return false;
	    } else {
	      return true;
	    }
	  }
Verify whether current token is a valid decimal token (which contains dot).
Returns true if the character that follows the token is not a digit or letter or underscore.

For example:
For char stream "2.3", "2." is not a valid decimal token, because it is followed by digit '3'.
For char stream "2.3_", "2.3" is not a valid decimal token, because it is followed by '_'.
For char stream "2.3W", "2.3" is not a valid decimal token, because it is followed by 'W'.
For char stream "12.0D 34.E2+0.12 "  12.0D is a valid decimal token because it is followed
by a space. 34.E2 is a valid decimal token because it is followed by symbol '+'
which is not a digit or letter or underscore.
amoro-format-mixed/amoro-mixed-spark/v3.2/amoro-mixed-spark-3.2/src/main/gen-antlr/org/apache/amoro/spark/sql/parser/MixedFormatSqlExtendLexer.java