Example: FindMaxElementInColumnIterative in Java

// FindMaxElementInColumnIterative
public class Main {

    /**
     * Finds the maximum element in a specified column of a 2D array.
     * Handles cases for empty matrices or invalid column indices.
     *
     * @param matrix The 2D integer array.
     * @param columnIndex The index of the column to search.
     * @return The maximum element in the specified column.
     * @throws IllegalArgumentException if the matrix is empty or columnIndex is invalid.
     */
    public static int findMaxInColumnIterative(int[][] matrix, int columnIndex) {
        // Step 1: Validate the matrix and column index
        if (matrix == null || matrix.length == 0 || matrix[0].length == 0) {
            throw new IllegalArgumentException("Matrix cannot be empty or null.");
        }
        if (columnIndex < 0 || columnIndex >= matrix[0].length) {
            throw new IllegalArgumentException("Invalid column index. Must be between 0 and " + (matrix[0].length - 1));
        }

        // Step 2: Initialize max_value with the first element of the column
        int max_value = matrix[0][columnIndex];

        // Step 3: Iterate through each row starting from the second row
        for (int i = 1; i < matrix.length; i++) {
            // Check if the current row is long enough to have the specified column
            if (matrix[i].length > columnIndex) {
                // Step 4: Compare current element with max_value and update if greater
                if (matrix[i][columnIndex] > max_value) {
                    max_value = matrix[i][columnIndex];
                }
            }
            // If the row is shorter, we effectively ignore it for this column search
        }

        // Step 5: Return the found maximum value
        return max_value;
    }

    public static void main(String[] args) {
        int[][] data = {
            {100, 150, 120, 180},
            {200, 190, 210, 170},
            { 90, 110, 130, 140},
            {300,  80, 250, 220}
        };

        // Example 1: Find max in column 1 (index 1)
        int targetColumn1 = 1;
        try {
            int maxInCol1 = findMaxInColumnIterative(data, targetColumn1);
            System.out.println("Max element in column " + targetColumn1 + ": " + maxInCol1);
        } catch (IllegalArgumentException e) {
            System.out.println("Error: " + e.getMessage());
        }

        // Example 2: Find max in column 0 (index 0)
        int targetColumn0 = 0;
        try {
            int maxInCol0 = findMaxInColumnIterative(data, targetColumn0);
            System.out.println("Max element in column " + targetColumn0 + ": " + maxInCol0);
        } catch (IllegalArgumentException e) {
            System.out.println("Error: " + e.getMessage());
        }

        // Example 3: Invalid column index
        int invalidColumn = 5;
        try {
            int maxInInvalidCol = findMaxInColumnIterative(data, invalidColumn);
            System.out.println("Max element in column " + invalidColumn + ": " + maxInInvalidCol);
        } catch (IllegalArgumentException e) {
            System.out.println("Error for invalid column " + invalidColumn + ": " + e.getMessage());
        }

        // Example 4: Empty matrix
        int[][] emptyMatrix = {};
        try {
            int maxInEmpty = findMaxInColumnIterative(emptyMatrix, 0);
            System.out.println("Max element in empty matrix: " + maxInEmpty);
        } catch (IllegalArgumentException e) {
            System.out.println("Error for empty matrix: " + e.getMessage());
        }
    }
}