TheAlgorithms/Java · error · IndexOutOfBoundsException

Invalid range indices

Error message

Invalid range indices

What it means

Thrown by PrefixSum.sumRange(left, right) when the query bounds are invalid: left < 0, right >= array length, or left > right. This is an IndexOutOfBoundsException because the indices would read past the prefix-sum buffer. Bounds are 0-based inclusive against the ORIGINAL array length (prefixSums.length - 1).

Source

Thrown at src/main/java/com/thealgorithms/prefixsum/PrefixSum.java:50

        for (int i = 0; i < array.length; i++) {
            // Automatically promotes int to long during addition
            this.prefixSums[i + 1] = this.prefixSums[i] + array[i];
        }
    }

    /**
     * Calculates the sum of elements in the range [left, right].
     * Indices are 0-based.
     *
     * @param left  The starting index (inclusive).
     * @param right The ending index (inclusive).
     * @return The sum of elements from index left to right as a long.
     * @throws IndexOutOfBoundsException if indices are out of valid range.
     */
    public long sumRange(int left, int right) {
        if (left < 0 || right >= prefixSums.length - 1 || left > right) {
            throw new IndexOutOfBoundsException("Invalid range indices");
        }
        return prefixSums[right + 1] - prefixSums[left];
    }
}

View on GitHub (pinned to fdfb9a395b)

Solutions

1. Pass inclusive 0-based indices: right should be lastIndex (length-1), not length.
2. Convert 1-based input to 0-based before calling.
3. Guard left >= 0 && right < array.length && left <= right at the caller.

Example fix

// before
long s = ps.sumRange(start, end); // end is exclusive here

// after
long s = ps.sumRange(start, end - 1); // end converted to inclusive index
// guard:
if (start < 0 || end - 1 >= n || start > end - 1) throw new IllegalArgumentException("bad range");

int n = array.length; // original data length
if (left < 0 || right >= n || left > right) {
    throw new IndexOutOfBoundsException("range [" + left + "," + right + "] invalid for size " + n);
}
long s = ps.sumRange(left, right);

static boolean validQuery(int left, int rightInclusive, int dataSize) {
    return left >= 0 && rightInclusive < dataSize && left <= rightInclusive;
}

try {
    long s = ps.sumRange(left, right);
} catch (IndexOutOfBoundsException e) {
    logger.warn("Bad range query [{}, {}]", left, right);
}

When it happens

Trigger: Call sumRange(0, array.length) (right past last index), sumRange(-1, 3), or sumRange(5, 2).

Common situations: Passing an exclusive end as inclusive (off-by-one); 1-based indices not converted; right computed as a list size rather than last index.

Related errors

• Invalid row indices
• Invalid column indices
• Invalid range: [%d, %d] for array of size %d
• Invalid range indices
• The index must not be negative.

AI-assisted analysis of TheAlgorithms/Java@fdfb9a395b (2026-08-13). Data as JSON: /api/errors/c5592fd4efded9f4. Report an issue: GitHub.