Is there a way to pass an API ArrayList field in POJO builder object?

I have this API request payload containing some nested fields:

 {
      "myId": "studentOne",
      "myFirstName": "joe",
      "myLastName": "bloggs",
      "demoPackages": 
       [{
          "myparts": "https://example.com/myparts/a1234567-5d25-9gf1-23ua-45pb3874265l",
          "myPackages": [
           "https:/example.com/myPackages/0sk98926-939a-444a-95ta-8eb40125f7r1"
            ]
        }
       ]
    }

I have this corresponding request model DTO:

@Data
@AllArgsConstructor
@NoArgsConstructor
@Builder
public class DemoRequest {
  private String myId;
  private String myFirstName;
  private String myLastName;
  private ArrayList<DemoPackage> demoPackages;


@Data
@AllArgsConstructor
@NoArgsConstructor
@Builder
  public class DemoPackage{
    private String myparts;
    private ArrayList myPackages;
  }
}

Now, the challenge. When creating a builder object that holds the API request, I am lost as to how to pass the ArrayList fields. I tried this:

public Object createMyPayload(String myId, String myFirstName, String myLastName, ArrayList myparts, ArrayList myPackages) { //not too sure if I am passing myParts and myPackages correctly here
    return DemoRequest.builder()
                         .myId(myId)
                         .myFirstName(myFirstName)
                         .myLastName(myLastName)
                         .releasePackages(myparts)
                         .releasePackages(myPackages)
                         .build();

When I call the createMyPayload() from another class to use the builder object, I am getting a compilation error which suggests that my ArrayList fields data type is wrong:

 @When("I send a POST request to the endpoint (.*)$")
public void create(String endpoint, String myId, String myFirstName, String myLastName, ArrayList myparts, ArrayList myPackages) {


String id = "studentOne"
String myFirstName = "joe"
String myLastName = "bloggs"
String myParts = "https://example.com/myparts/a1234567-5d25-9gf1-23ua-45pb3874265l";
String myPackages = "https:/example.com/myPackages/0sk98926-939a-444a-95ta-8eb40125f7r1";


    demoClass.post(createPayload.createMyPayload(myId, myFirstName, myLastName, myParts, myPackages), endpoint); // myParts and myPackages throw compilation error that data should be Arraylist but when I change to ArrayList, it's asking me to change back to String

How do I correctly pass myParts and myPackages to the lombok builder object and reuse them elsewhere?

This should work.

Note that I have used ArrayList & Array where [] would be better, but you mentioned API using ArrayList. Used List in declarations rather than ArrayList (because that's better practise)

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

public class PackageBuilderDemo {
	
	public static void main(String[] args) {
		PackageBuilderDemo packageBuilderDemo = new PackageBuilderDemo();
		packageBuilderDemo.createMyPayload("studentOne", "joe", "bloggs", "https://example.com/myparts/a1234567-5d25-9gf1-23ua-45pb3874265l", Arrays.asList(new String[] {"https:/example.com/myPackages/0sk98926-939a-444a-95ta-8eb40125f7r1"}));
	}
	
	public DemoRequest createMyPayload(String myId, String myFirstName, String myLastName, String myParts, List<String> myPackages) { 
	    DemoPackage demoPackage = DemoPackage.builder().myparts(myParts).myPackages(myPackages).build();
		List<DemoPackage> demoPackages = new ArrayList<>();
				demoPackages.add(demoPackage);
		return DemoRequest.builder()
	                         .myId(myId)
	                         .myFirstName(myFirstName)
	                         .myLastName(myLastName)
	                         .demoPackages(demoPackages)
	                         .build();
	}

}


@Data
@AllArgsConstructor
@NoArgsConstructor
@Builder
public class DemoRequest {
  private String myId;
  private String myFirstName;
  private String myLastName;
  private List<DemoPackage> demoPackages;
  
}


@Data
@AllArgsConstructor
@NoArgsConstructor
@Builder
public class DemoPackage{
    private String myparts;
    private List<String> myPackages;
  }

could be done by directly converting array to list.

return DemoRequest.builder()
.myId(myId)
.myFirstName(myFirstName)
.myLastName(myLastName)
.Arrays.asList(demoPackages(DemoPackage.builder()
.myparts(myParts)
.myPackages(myPackages)
.build()))
.build();