Please explain the following methods in details

public class Task1 {   public static void main(String[] args) {     double[] nums1d = {1, 3};     double[][] nums1 = {{1, 2}, {3, 4, 5}, {6}};     double[][] nums2 = {{4, 6}, {12, 4, 5}, {6}};     String str = "abc";     String[] str2 = {"Hello", "World"};     String[][] str3 = {{"Hello", "World"}, {"Welcome", "to", "Java"}}; } /**   * This method calculates max double in 2d array   *   * @param nums1 {{1,2},{3,4,5},{6}}   * @return max {6}   */   public static double max(double[][] nums1) {     double max = 0;     for (double[] nums : nums1) {       for (double num : nums) {         if (num > max) {           max = num;         }       }     }     return max;   }   /**   * This method calculates max double of each row   *   * @param nums1 {{1,2},{3,4,5},{6}}   * @return maxRow {2,5,6}   */   public static double[] maxRow(double[][] nums1) {     double[] maxRow = new double[sumRow(nums1).length];     double idx = 0;     for (int i = 0; i < sumRow(nums1).length; i++) {       for (double num : nums1[i]) {         if (num > idx) {           idx = num;         }       }       maxRow[i] = idx;       idx = 0;     }     return maxRow;   }   /**   * This method calculates max double of each column   *   * @param nums1 {{1,2},{3,4,5},{6}}   * @return maxCol {6,4,5}   */   public static double[] maxCol(double[][] nums1) {     double[] maxCol = new double[sumCol(nums1).length];     double idx = 0;     for (int i = 0; i < sumCol(nums1).length; i++) {       for (double[] nums : nums1) {         if (nums.length > i) {           if (nums[i] > idx) {             idx = nums[i];           }         }       }       maxCol[i] = idx;       idx = 0;     }     return maxCol;   }   /**   * This method counts the number of vowels in a string   *   * @param str ["abc"]   * @return no of vowels {1}   */   public static int countVowels(String str) {     int vowels = 0;     for (int i = 0; i < str.length(); i++) {       char ch = str.charAt(i);       Character.toUpperCase(ch);       if (ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u') {         vowels++;       }     }     return vowels;   }   /**   * This method counts the number of vowels in a 1d string array   *   * @param str2 {"Hello", "World"}   * @return no of vowels in 1d array {3}   */   public static int countVowelsArray(String[] str2) {     int vowels = 0;     for (String word : str2) {       countVowels(word);       vowels += countVowels(word);     }     return vowels;   }   /**   * This method counts the number of vowels in a 2d string array   *   * @param str3 {"Hello", "World"}, {"Welcome", "to", "Java"}   * @return no of vowels in 2d string {9}   */   public static int countVowelsTwoDArray(String[][] str3) {     int vowels = 0;     for (String[] words : str3) {       countVowelsArray(words);       vowels += countVowelsArray(words);     }     return vowels;   }