How to use Stream API with list of object array?

i have this method given below... how can i change this method in stream api.

public List<AddNewSchoolBean> getEmployeeList() {

		List<AddNewSchoolBean> list = new ArrayList<>();

		try {
			List<Object[]> empList = null;

			empList = Dao.getEmpDetailsFromUserMst();

			if (empList.size() != 0) {
				for (Object[] obj : empList) {
					AddNewSchoolBean bean = AddNewSchoolBean.builder()
							.employeeId((obj[0]).toString())
							.employeeName((obj[1]).toString())
							.schoolName((obj[2]).toString())
							.build();
					list.add(bean);
				}
			}

		} catch (Exception e) {
			e.printStackTrace();
		}
		return list;
	}

Assuming you want to internally use a java.util.Stream I would suggest first to polish/cleanup your code a bit.

1. You don't need to split declaration and assignment of the empList variable
2. Move the conversion logic into a private method.
3. The if check for size doesn't add anything.

public List<AddNewSchoolBean> getEmployeeList() {

    List<AddNewSchoolBean> list = new ArrayList<>();

    try {
        List<Object[]> empList = Dao.getEmpDetailsFromUserMst();
        for (Object[] obj : empList) {         
            AddNewSchoolBean bean = convert(obj);
            list.add(bean);        
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
    return list;
}

private AddNewSchoolBean convert(Object[] empArray) {
  return AddNewSchoolBean.builder()
                    .employeeId((empArray[0]).toString())
                    .employeeName((empArray[1]).toString())
                    .schoolName((empArray[2]).toString())
                    .build();
}

Now assuming you cannot change the Dao.getEmpDetailsFromUserMst(); you can use the stream() method on the List to convert it to a java.util.Stream. Then you can use map to convert the array into an object and finally collect to a list and return it.

public List<AddNewSchoolBean> getEmployeeList() {
        List<Object[]> empList = Dao.getEmpDetailsFromUserMst();
        return empList.stream()
                   .map(this::convert)
                   .toList();
}

This is assuming you are on JDK17 and you need ofcourse the aforementioned convert method.

I think the clean way is to map it to AddNewSchoolBean and then collect into List:

public List<AddNewSchoolBean> getEmployeeList() {
    try {
        List<Object[]> empList = Dao.getEmpDetailsFromUserMst();

        return empList.stream()
                .map(this::createAddNewSchoolBean)
                .collect(Collectors.toList());

    } catch (Exception e) {
        e.printStackTrace();
    }
    return Collections.emptyList();
}

private AddNewSchoolBean createAddNewSchoolBean(Object[] obj) {
    return AddNewSchoolBean.builder()
            .employeeId(String.valueOf(obj[0]))
            .employeeName(String.valueOf(obj[1]))
            .schoolName(String.valueOf(obj[2]))
            .build();
}

You can simplify even to this

@SneakyThrows
public List<AddNewSchoolBean> getEmployeeList() {
    return emptyIfNull(Dao.getEmpDetailsFromUserMst())
            .stream()
            .map(AddNewSchoolBean::new)
            .toList();
}

And your AddNewSchoolBean to have Object constructor

public class AddNewSchoolBean{
   String employeeId;
   String employeeName;
   String schoolName;

   public AddNewSchoolBean(Object[] data) {
       this.employeeId = String.valueOf(data[0]);
       this.employeeName = String.valueOf(data[1]);
       this.schoolName = String.valueOf(data[2]);
   }
}

Some additional imports required to make it simpler

import lombok.SneakyThrows;
import static org.apache.commons.collections4.ListUtils.emptyIfNull;

In this Lambda expression, you first make sure your collection is not null, by using emptyIfNull (can be empty, but doesn't throw NPE), and then you stream through collection and map it to AddNewSchoolBean bean/entity via constructor. You can of course use with if you wish, but this looks cleaner. And then in the end you collect to List. Pleas note this is Immutable result, if you need Mutable, use .collect(Collectors.toList())