Hey Rajesh, you can check this code snippet to understand desired capabilities methods on a webdriver:
public class Desired_Capability_Methods {
  public static void main(String[] args) throws IOException {
  System.setProperty("webdriver.gecko.driver", "D:\\geckodriver.exe");
  WebDriver driver = new FirefoxDriver();
  driver.get("https://www.google.com/");
  // Created DesiredCapabilities object
  DesiredCapabilities capabilities = new DesiredCapabilities();
  capabilities.setCapability("deviceName", "your Device Name");
  capabilities.setCapability(CapabilityType.BROWSER_NAME, "Chrome");
  capabilities.setCapability(CapabilityType.VERSION, "5.1");
  capabilities.setCapability("platformName", "Android");
  }
}