public int getMinElement() {
		if ( isNil() ) {
			throw new RuntimeException("set is empty");
		}

		return intervals.get(0).a;
	}
Returns the minimum value contained in the set if not isNil().

@return the minimum value contained in the set.
@throws RuntimeException if set is empty
runtime/Java/src/org/antlr/v4/runtime/misc/IntervalSet.java