CODEWITHSUNDEEP
javaobjectnullpointerexceptionnullhashmap
java123999
java123999

Reputation: 7394

NPE when populating HashMap within an object?

I have the following object:

public class PersonDTO {

    private Map<String, String> idsAndNames;

    //default constructor
    public PersonDTO() {
    }

    public PersonDTO(Map<String, String> idsAndNames) {
        this.idsAndNames = idsAndNames;
    }

    public void setIdsAndNames(Map<String, String> idsAndNames) {
        this.idsAndNames = idsAndNames;
    }

    public Map<String, String> getIdsAndNames() {
        return idsAndNames;
    }


    public void addEntryToMap(String id, String name) {
        this.idsAndNames.put(id, name);
    }

}

Whenever I try to populate the map within the object (see method below), I get a Null Pointer Exception saying that the Map is null. How can I fix this?

Method to populate object (within main class):

public PersonDTO populatePersonDTO(List<String> ids, List<String> names){

        Map<String, String> idsAndNames = new HashMap<>();
        PersonDTO personDTO = new PersonDTO();
        personDTO.setIdsAndNames(idsAndNames);

        for(int i=0;i<ids.size();i++){

            personDTO.addEntryToMap(ids.get(i),names.get(i)); //line throwing NPE
        }
        return personDTO;
    }

Calling populatePersonDTO:

List<String> ids= Arrays.asList("1", "2", "3");
List<String> names= Arrays.asList("name1", "name2", "name3");

populatePersonDTO(ids, names);

Upvotes: 0

Views: 62

Answers (1)

walen
walen

Reputation: 7273

If the NPE line points to populatePersonDTO, then names is the one being null (ids can't be since we're calling ids.size() w/o problem). If it was idsAndNames the NPE would point to addEntryToMap instead.

So make sure that names is not null.

Upvotes: 1

Related Questions