public Builder<T> identifiers(final Predicate<? super T> identifiers) {
			_identifiers = requireNonNull(identifiers);
			return this;
		}
Set the predicate which defines identifier tokens.

@param identifiers the identifier predicate
@return {@code this} builder, for method chaining
@throws NullPointerException if the {@code identifiers} is {@code null}
jenetics.ext/src/main/java/io/jenetics/ext/internal/util/FormulaParser.java