Various ways to check is a 2-dimensional ArrayList contains a specified value

Contains.java

import java.util.List;
import java.util.ArrayList;


import java.util.Arrays;
import java.util.Objects;
import java.util.stream.Collectors;

public class Contains {

//------------------------------------------------------------------------------

  public static boolean contains4(List< ArrayList<String> > matrix, Object obj) {

    // 1. Get a stram of lists
    // 2. Flatten them into a single map
    // 3. Apply condition that at least one match

    return matrix.stream()
                 .flatMap(List::stream)
                 .anyMatch(o ->

                    Objects.equals(o, obj)
                 );
  }

//------------------------------------------------------------------------------

  public static boolean contains3(List< ArrayList<String> > matrix, Object obj) {

    // 1. Get a stream of lists
    // 2. Flatten them into a single map
    // 3. Convert to a list
    // 4. Perform liean search on the list

    return matrix.stream()
                 .flatMap(List::stream)
                 .collect(Collectors.toList())
                 .contains(obj);
  }

//------------------------------------------------------------------------------

  public static boolean contains2(List< ArrayList<String> > matrix, Object obj) {

    // Iterate over all rows
    for (List<?> row : matrix) {

      // Iterate over each value per row
      for (Object o : row) {

        // Compare
        if (Objects.equals(o, obj)) {

          return true;
        }
      }
    }

    return false;
  }

//------------------------------------------------------------------------------

  public static boolean contains1(List< ArrayList<String> > matrix, Object obj) {

    // 1. Check if the matrix is empty
    if (matrix.isEmpty()) {

      return false;
    }

    // 2. Get matrix dimensions
    int rows = matrix.size();
    int cols = matrix.get(0).size();

    Object temp;

    // Loop from 0 to row count
    for (int i = 0; i < rows; i++) {

      // Loop from 0 to column count
      for (int j = 0; j < cols; j++) {

        // Get matrix[i][j]
        temp = matrix.get(i).get(j);

        // Compare
        if (Objects.equals(obj, temp)) {

          return true;
        }
      }

    }

    return false;
  }

//------------------------------------------------------------------------------

  public static void main(String[] args) {

    var row    = new ArrayList<String>();

    row.add("A");
    row.add("B");
    row.add("C");

    var matrix = new ArrayList< ArrayList<String> >();

    matrix.add(row);
    matrix.add(row);
    matrix.add(row);

    test(matrix, "A");

    for (List<?> r : matrix) {

      r.remove("A");
    }

    test(matrix, "A");
  }

//------------------------------------------------------------------------------

  public static void display(List< ArrayList<String> > matrix) {

    for (List<String> r : matrix) {

      System.out.println(r);
    }
  }

//------------------------------------------------------------------------------

  public static void test(List< ArrayList<String> > matrix, Object obj) {

    display(matrix);

    System.out.format(
      "--------------------\n" +
      "contains1(%s) = %s\n"   +
      "contains2(%s) = %s\n"   +
      "contains2(%s) = %s\n"   +
      "contains2(%s) = %s\n"   +
      "--------------------\n\n",
      obj, contains1(matrix, obj),
      obj, contains2(matrix, obj),
      obj, contains3(matrix, obj),
      obj, contains4(matrix, obj)
    );
  }

}