antlr/antlr4 · error · RuntimeException

set is empty

Error message

set is empty

What it means

Error "set is empty" thrown in antlr/antlr4.

Source

Thrown at runtime/Java/src/org/antlr/v4/runtime/misc/IntervalSet.java:421

		}
		return false;
    }

    /** {@inheritDoc} */
    @Override
    public boolean isNil() {
        return intervals==null || intervals.isEmpty();
    }

	/**
	 * Returns the maximum value contained in the set if not isNil().
	 *
	 * @return the maximum value contained in the set.
	 * @throws RuntimeException if set is empty
	 */
	public int getMaxElement() {
		if ( isNil() ) {
			throw new RuntimeException("set is empty");
		}
		Interval last = intervals.get(intervals.size()-1);
		return last.b;
	}

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

		return intervals.get(0).a;
	}

View on GitHub (pinned to 7d5770395b)

Solutions

1. Call size() (or isEmpty()) before calling getMin() so you never read the minimum of an empty set.
2. Guard the call: if (!set.isEmpty()) { Interval min = set.getMin(); }.
3. If the set may legitimately be empty, handle that branch explicitly instead of asking for its minimum.

Example fix

IntervalSet set = new IntervalSet();
if (set.isEmpty()) {
    // handle empty case, e.g. skip or use a default
} else {
    Interval min = set.getMin();
}

When it happens

Trigger: Thrown by IntervalSet.minElement()/maxElement() when the set contains no intervals.

Common situations: Check set.isNil()/size>0 before calling minElement or maxElement; guard against empty IntervalSet after filtering or subtraction operations.

AI-assisted analysis of antlr/antlr4@7d5770395b (2026-08-14). Data as JSON: /api/errors/dbc2e92a67072830. Report an issue: GitHub.