import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.stream.Collectors;

public class Main {

    public static void main(String[] args) {
	// write your code here
        List<Object[]> list = new ArrayList<>();

        Object[] ar = {123,null};
        Object[] arr = {321,null};
        list.add(ar);
        list.add(arr);

        Map<Integer, String> collect = list.stream()
                .filter(Objects::nonNull)
                .collect(Collectors.toMap(obj -> (Integer)obj[0], obj -> (String)obj[1]));

        System.out.println(collect);
    }
}