Map an object in List

Question

Assume the getter() method returns List<Object>. Assume the Object class has getFirstName(), getLastName(), and trying to do the following.

public List<<String,String>> getSomethingElse(@QueryParam("Id") Long Id) {
    getter(id).stream().map(p -> new PDropDown<Object>(?).collect(Collectors.toList());

I want this to return only firstName and LastName. How can I map the object so it returns only those two?

`List<>` what is this type ? – davidxxx Aug 09 '18 at 15:31 — davidxxx, Aug 09 '18 at 15:31
Please provide compilable code that can be analyzed. – Luiggi Mendoza Aug 09 '18 at 15:32 — Luiggi Mendoza, Aug 09 '18 at 15:32

davidxxx · Accepted Answer · 2018-08-09T15:46:36.373

Note that the getter() method has to return a specific type for example List<Person> rather than List<Object> otherwise you have to cast it.
The idea would be to map firstName and the lastName to a PDropDown instance that provides a constructor that accepts them :

You could do that :

List<DropDown> result =  
    getter(id).stream()
              .map(p -> new PDropDown(p.getFirstName(), p.getLastName()))
              .collect(Collectors.toList());

If getter() returns List<Object>, you could throw an exception if one of the elements returned is not a Person :

List<DropDown> result =  
    getter(id).stream()
              .map( o -> { if (o instanceof Person){
                             Person p = (Person) o;
                             return new PDropDown(p.getFirstName(), p.getLastName()); 
                          }
                          throw new IllegalArgumentException("o "+ o + " is not a Person");
                         })
              .collect(Collectors.toList());

Map an object in List

1 Answers1