List<List<String>> table
List<Map<String, String>> table
Map<String, String> table
Map<String, List<String>> table
Map<String, Map<String, String>> table

| firstName | lastName | age |
| Thomas    | Brown | 30 |
| Perry     | Wilson | 26 |
| Ashley    | William | 27 |

java type: List<List<String>>

The natural representation of list of a list of strings is shown below.

[ 
  [ "firstName", "lastName", "age" ],
  [ "Thomas", "Brown", "30" ], 
  [ "Perry", "Wilson", "26" ], 
  [ "Ashley", "William", "27" ] 
]

java type: List<Map<String, String>>
The natural representation of list of maps is shown below.

[
  { "firstName": "Thomas", "lastName": "Brown",  "age": "30" }, 
  { "firstName": "Perry",  "lastName": "Wilson", "age": "26" }, 
  { "firstName": "Ashley", "lastName": "William", "age": "27" } 
]

Table where first colum is key as shown below

| IN  | India          |
| IRE | Ireland        |
java type: Map<String, String>

TO convert the table into a single map

{
  "IN": "India",
  "IRE": "Ireland"
}

 A table with multiple column values per key.
 
 | IN  | India          | 29  |
 | IRE | Ireland        | 8   |

java type: Map<String, List<String>>

{
  "IN":  ["India","29"],
  "IRE": ["Ireland","8"]
}

Feature: Login to HRM Application 
 
  @ValidCredentials
  Scenario: Login with valid credentials - Data Table without Header

    Given User is on HRMLogin page
    When User enters valid credentials
      | Admin | admin123 |
    Then User should be able to login successfully and new page open

import io.cucumber.datatable.DataTable;
import io.cucumber.java.After;
import io.cucumber.java.Before;
import io.cucumber.java.en.Given;
import io.cucumber.java.en.Then;
import io.cucumber.java.en.When;
import org.junit.Assert;
import org.openqa.selenium.By;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.chrome.ChromeDriver;
import java.util.List;
import java.util.Map;
import java.util.concurrent.TimeUnit;
import static org.hamcrest.CoreMatchers.containsString;
import static org.hamcrest.MatcherAssert.assertThat;

public class DataTableDefinitions {

    WebDriver driver;

 @Before
    public void setup() {

        ChromeOptions options = new ChromeOptions();
        options.addArguments("--start-maximized");
        driver = new ChromeDriver(options);
        driver.manage().timeouts().implicitlyWait(Duration.ofSeconds(5));

    }

    @Given("User is on HRMLogin page")
    public void userOnHomePage() {

        driver.get("https://opensource-demo.orangehrmlive.com/");
    }

     @When("User enters valid credentials")
    public void entersValidCredential(DataTable dataTable) throws InterruptedException{

        System.out.println("Credentials Entered");

        List<List<String>> signUpForm = dataTable.asLists(String.class);
        String userName = signUpForm.get(0).get(0);
        String passWord = signUpForm.get(0).get(1);
        driver.findElement(By.name("username")).sendKeys(userName);
        driver.findElement(By.name("password")).sendKeys(passWord);
        driver.findElement(By.xpath("//*[@class='oxd-form']/div[3]/button")).submit();
    }

    @Then("User should be able to login successfully and new page open")
    public void successfulLogin() throws InterruptedException {

        String newPageText = driver.findElement(By.xpath("//*[@class='oxd-topbar-header-breadcrumb']/h6")).getText();
        System.out.println("newPageText :" + newPageText);
        assertThat(newPageText, containsString("Dashboard"));
    }

    @After
    public void teardown(){
        driver.quit();
    }
}

import io.cucumber.junit.Cucumber;
import io.cucumber.junit.CucumberOptions;
import org.junit.runner.RunWith;

@RunWith(Cucumber.class)
@CucumberOptions(monochrome = true, plugin = "pretty", features = "src/test/resources/Features/DataTable.feature",
        glue = "definitions", tags="@ValidCredentials")

public class CucumberRunnerTest {
}

  @InValidCredential
  Scenario: Login with invalid credential - Header with Single Row

    Given User is on HRMLogin page
    Then User enters invalid credentials and Login will be unsuccessful with error message
      | Username  | Password   | ErrorMessage        |
      | Admin1    | admin123!$ | Invalid credentials |

package org.example.definitions;

import io.cucumber.datatable.DataTable;
import io.cucumber.java.After;
import io.cucumber.java.Before;
import io.cucumber.java.en.Given;
import io.cucumber.java.en.Then;
import io.cucumber.java.en.When;
import org.junit.Assert;
import org.openqa.selenium.By;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.chrome.ChromeDriver;
import org.openqa.selenium.chrome.ChromeOptions;

import java.time.Duration;
import java.util.List;
import java.util.Map;

public class DataTableDefinitions {

    WebDriver driver;

    @Before
    public void setup() {

        ChromeOptions options = new ChromeOptions();
        options.addArguments("--start-maximized");
        driver = new ChromeDriver(options);
        driver.manage().timeouts().implicitlyWait(Duration.ofSeconds(5));

    }

    @Given("User is on HRMLogin page")
    public void userOnHomePage() {

        driver.get("https://opensource-demo.orangehrmlive.com/");
    }

    @Then("User enters invalid credentials and Login will be unsuccessful with error message")
    public void entersInvalidCredential(DataTable userTable) throws InterruptedException {

        System.out.println("Enter Credentials");
        List<Map<String, String>> user = userTable.asMaps(String.class, String.class);

        String userName = user.get(0).get("Username");
        System.out.println("Username :" + userName);
        driver.findElement(By.name("username")).sendKeys(userName);

        String passWord = user.get(0).get("Password");
        System.out.println("Password :" + passWord);
        driver.findElement(By.name("password")).sendKeys(passWord);

        driver.findElement(By.xpath("//*[@class='oxd-form']/div[3]/button")).submit();

        String errorMessage = user.get(0).get("ErrorMessage");
        String actualErrorMessage = driver.findElement(By.xpath("//*[@class='orangehrm-login-error']/div[1]/div[1]/p")).getText();
        System.out.println("Actual Error Message :" + actualErrorMessage);
        Assert.assertTrue(actualErrorMessage.equalsIgnoreCase(errorMessage));

    }

    @After
    public void teardown(){
        driver.quit();
    }

}

  @Multiple_InValidCredentials
  Scenario: Login with invalid credentials - Data Table with Header and Multiple Rows

    Given User is on HRMLogin page
    Then User enters invalid credentials and Login will be unsuccessful with custom error messages
      | Username    | Password  | ErrorMessage         |
      | Admin1      | admin123! | Invalid credentials  |
      | Admina      | admin123a | Invalid credentials  |
   

import io.cucumber.datatable.DataTable;
import io.cucumber.java.After;
import io.cucumber.java.Before;
import io.cucumber.java.en.Given;
import io.cucumber.java.en.Then;
import io.cucumber.java.en.When;
import org.junit.Assert;
import org.openqa.selenium.By;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.chrome.ChromeDriver;
import java.util.List;
import java.util.Map;
import java.util.concurrent.TimeUnit;
import static org.hamcrest.CoreMatchers.containsString;
import static org.hamcrest.MatcherAssert.assertThat;

public class DataTableDefinitions {

    WebDriver driver;

     @Before
    public void setup() {

        ChromeOptions options = new ChromeOptions();
        options.addArguments("--start-maximized");
        driver = new ChromeDriver(options);
        driver.manage().timeouts().implicitlyWait(Duration.ofSeconds(5));

    }

    @Given("User is on HRMLogin page")
    public void userOnHomePage() {

        driver.get("https://opensource-demo.orangehrmlive.com/");
    }

     @Then("User enters invalid credentials and Login will be unsuccessful with custom error messages")
    public void entersInvalidCredentials(DataTable userTable) throws InterruptedException {

        System.out.println("Enter Credentials");

        List<Map<String, String>> user = userTable.asMaps(String.class, String.class);
        for (Map<String, String> form : user) {

            String userName = form.get("Username");
            System.out.println("Username :" + userName);
            driver.findElement(By.name("username")).sendKeys(userName);

            String passWord = form.get("Password");
            System.out.println("Password :" + passWord);
            driver.findElement(By.name("password")).sendKeys(passWord);

            driver.findElement(By.xpath("//*[@class='oxd-form']/div[3]/button")).submit();

            String errorMessage = form.get("ErrorMessage");
            String actualErrorMessage = driver.findElement(By.xpath("//*[@class='orangehrm-login-error']/div[1]/div[1]/p")).getText();
            System.out.println("Actual Error Message :" + actualErrorMessage);

            Assert.assertTrue(actualErrorMessage.equalsIgnoreCase(errorMessage));

        }
    }

    @After
    public void teardown(){
        driver.quit();
    }

}