TheAlgorithms/Java · error · IllegalArgumentException

Input array cannot be null or empty.

Error message

Input array cannot be null or empty.

What it means

Thrown by WineProblem.wpbu(int[] arr) when arr is null or empty. The bottom-up DP allocates strg = new int[n][n] where n = arr.length; an empty array yields a degenerate 0x0 table and null NPEs on access. Message: 'Input array cannot be null or empty.'

Source

Thrown at src/main/java/com/thealgorithms/dynamicprogramming/WineProblem.java:88

        int start = wptd(arr, si + 1, ei, strg) + arr[si] * year;
        int end = wptd(arr, si, ei - 1, strg) + arr[ei] * year;

        int ans = Math.max(start, end);
        strg[si][ei] = ans;

        return ans;
    }

    /**
     * Calculate maximum profit using bottom-up dynamic programming with tabulation.
     *
     * @param arr Array of wine prices.
     * @throws IllegalArgumentException if the input array is null or empty.
     * @return Maximum profit obtainable by selling the wines.
     */
    public static int wpbu(int[] arr) {
        if (arr == null || arr.length == 0) {
            throw new IllegalArgumentException("Input array cannot be null or empty.");
        }
        int n = arr.length;
        int[][] strg = new int[n][n];

        for (int slide = 0; slide <= n - 1; slide++) {
            for (int si = 0; si <= n - slide - 1; si++) {
                int ei = si + slide;
                int year = (n - (ei - si + 1)) + 1;
                if (si == ei) {
                    strg[si][ei] = arr[si] * year;
                } else {
                    int start = strg[si + 1][ei] + arr[si] * year;
                    int end = strg[si][ei - 1] + arr[ei] * year;

                    strg[si][ei] = Math.max(start, end);
                }
            }
        }

View on GitHub (pinned to fdfb9a395b)

Solutions

1. Ensure the array has at least one element before calling wpbu.
2. Validate arr != null && arr.length > 0 at the boundary.
3. Default to a sensible non-empty input or report the empty source upstream.

Example fix

// before
int profit = WineProblem.wpbu(arr);

// after
if (arr == null || arr.length == 0) throw new IllegalArgumentException("prices required");
int profit = WineProblem.wpbu(arr);

if (arr == null || arr.length == 0) {
    throw new IllegalArgumentException("wine prices required");
}
WineProblem.wpbu(arr);

arr != null && arr.length > 0

When it happens

Trigger: Passing null or an empty price array; loading wine prices from an empty source; uninitialized array field.

Common situations: Reading prices from a config/file that was empty; tests with an empty fixture; refactoring that left the array unset.

Related errors

• Keys and frequencies cannot be null
• Price array cannot be null or empty.
• Input string must not be null
• Input array should not contain negative number(s).
• Keys and frequencies must have the same length

AI-assisted analysis of TheAlgorithms/Java@fdfb9a395b (2026-08-13). Data as JSON: /api/errors/b7d9abb7a7493c76. Report an issue: GitHub.