TheAlgorithms/Java · error · IllegalArgumentException

Given range of values is invalid!

Error message

Given range of values is invalid!

What it means

Thrown by AmicableNumber.findAllInRange when the range is structurally invalid: from<=0 OR to<=0 OR to<from. Amicable numbers are defined on positive integers and the search is a nested loop from i..to, so a non-positive endpoint or an inverted range is rejected before any work.

Source

Thrown at src/main/java/com/thealgorithms/maths/AmicableNumber.java:34

 * link: https://en.wikipedia.org/wiki/Amicable_numbers
 * <p>
 * Simple Example: (220, 284)
 * 220 is divisible by {1,2,4,5,10,11,20,22,44,55,110} <-SUM = 284
 * 284 is divisible by {1,2,4,71,142} <-SUM = 220.
 */
public final class AmicableNumber {
    private AmicableNumber() {
    }
    /**
     * Finds all the amicable numbers in a given range.
     *
     * @param from range start value
     * @param to   range end value (inclusive)
     * @return list with amicable numbers found in given range.
     */
    public static Set<Pair<Integer, Integer>> findAllInRange(int from, int to) {
        if (from <= 0 || to <= 0 || to < from) {
            throw new IllegalArgumentException("Given range of values is invalid!");
        }

        Set<Pair<Integer, Integer>> result = new LinkedHashSet<>();

        for (int i = from; i < to; i++) {
            for (int j = i + 1; j <= to; j++) {
                if (isAmicableNumber(i, j)) {
                    result.add(Pair.of(i, j));
                }
            }
        }
        return result;
    }

    /**
     * Checks whether 2 numbers are AmicableNumbers or not.
     */
    public static boolean isAmicableNumber(int a, int b) {

View on GitHub (pinned to fdfb9a395b)

Solutions

1. Supply a valid positive, ordered range: findAllInRange(1, 1000).
2. Normalize bounds before calling: lo=min(a,b), hi=max(a,b), then reject if lo<=0.
3. Validate user input and show a field error instead of forwarding to the API.

Example fix

// before
Set<?> r = AmicableNumber.findAllInRange(start, end);
// after
int lo = Math.min(start, end), hi = Math.max(start, end);
if (lo <= 0) throw new IllegalArgumentException("range start must be positive");
Set<?> r = AmicableNumber.findAllInRange(lo, hi);

int lo = Math.min(from, to), hi = Math.max(from, to);
if (lo <= 0) {
    throw new IllegalArgumentException("range must be within positive integers");
}
Set<?> r = AmicableNumber.findAllInRange(lo, hi);

static boolean isValidRange(int from, int to) {
    return from > 0 && to > 0 && from <= to;
}

try {
    Set<?> r = AmicableNumber.findAllInRange(from, to);
} catch (IllegalArgumentException e) {
    // bad range; ask the user for corrected bounds
}

When it happens

Trigger: findAllInRange(0, 10); findAllInRange(-3, 5); findAllInRange(10, 5) (inverted); findAllInRange where both bounds come from user input with no ordering check.

Common situations: UI range inputs where the user left 'from' blank (parses to 0); swapping min/max in the caller; inclusive-vs-exclusive bound confusion producing to<from.

Related errors

• Numbers array cannot be empty or null
• Number must be positive.
• Input numbers must be natural!
• Side length must be greater than 0
• Length must be greater than 0

AI-assisted analysis of TheAlgorithms/Java@fdfb9a395b (2026-08-13). Data as JSON: /api/errors/e4b453ba9b844916. Report an issue: GitHub.