import java.io.File; import java.io.FileNotFoundException;  import java.util.ArrayList; import java.util.HashMap; import java.util.Map; import java.util.Scanner;  public class BuildTableWithArrays {      private static final String separator = "\\s+" // regex for parsing lines     private static final int rowWidth = 4;      public static void main(String[] args) {          Map<Integer, ArrayList<String>> columns = buildMapWithColumnArrayLists("animals.txt");         printMap(columns);  // for demo         // if you want actual arrays         Map<Integer, String[]> colArrays = buildMapWithColumnArrays(columns);      }      public static Map<Integer, ArrayList<String>> buildMapWithColumnArrayLists(         String fileName) {          ArrayList<String> col0 = new ArrayList<String>();         ArrayList<String> col1 = new ArrayList<String>();         ArrayList<String> col2 = new ArrayList<String>();         ArrayList<String> col3 = new ArrayList<String>();          Map<Integer, ArrayList<String>> columns = new HashMap<Integer, ArrayList<String>>();         columns.put(0, col0);         columns.put(1, col1);         columns.put(2, col2);         columns.put(3, col3);          File file = new File(fileName);         try {             Scanner input = new Scanner(file);             while (input.hasNextLine()) {                 String[] line = input.nextLine().trim().replaceAll(separator, " ")                     .split(separator);                 for (int i = 0; i < rowWidth; i++) {                     if (line[i] == null) {                         columns.get(Integer.valueOf(i)).add("null");                     } else {                         columns.get(Integer.valueOf(i)).add(line[i]);                     }                 }             }             input.close();         } catch (FileNotFoundException x) {             System.out.println(x.getMessage());         }          return columns;     }      public static void printMap(Map<Integer, ArrayList<String>> columns) {          for (int i = 0; i < rowWidth; i++) {             System.out.println("col" + i + " #elements = "                 + columns.get(Integer.valueOf(i)).size());             for (String s : columns.get(Integer.valueOf(i))) {                 System.out.print(s + " ");             }             System.out.println("\n");         }     }      public static String[] convertArrayList2Array (ArrayList<String> arrayList) {          String[] array = new String[arrayList.size()];         array = arrayList.toArray(array);         return array;      }      public static Map<Integer, String[]> buildMapWithColumnArrays(Map<Integer, ArrayList<String>> columns) {          Map<Integer, String[]> cols = new HashMap<Integer, String[]>();           for (Map.Entry<Integer, ArrayList<String>> entry : columns.entrySet()) {             Integer key = entry.getKey();             ArrayList<String> value = entry.getValue();             String[] val = convertArrayList2Array(value);             cols.put(key,val);         }          return cols;      }  }

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