Pulling only certain objects from an array based on the values of another array of strings

Question

I am working on an android project in java. I have an array of objects that looks like this

Agenda = [{id: 1, sessionName: Some name, sessionLocation: Some place},
         {id: 2, sessionName: Some name, sessionLocation: Some place},
         {id: 3, sessionName: Some name, sessionLocation: Some place}]

I also have an array of strings that is dynamic, so it can have several values... looks like this:

sessionID = {1, 3}

How can I check for these sessionIDs within the "id" field in the Agenda array and pull only these objects where the ids match into a new array.

Note:

This is java not javascript
"id" in the Agenda array objects is an int
sessionID array is an array of string

I tried several examples but none of them worked!

filter is your friend - take a look at stackoverflow.com/questions/47787247/… — user2637293
– user2637293, Commented Jun 7, 2019 at 7:58
Hi @user2637293, can you give me a update to see if this solves. — Brother
– Brother, Commented Jun 14, 2019 at 14:39

Brother · Accepted Answer · 2019-06-17 06:12:15Z

1

[UPDATED] Example for Arraylist:

If you are using Java 8, consider the following setup:

List<Agenda> agenda = new ArrayList<Agenda>();
agenda.add(new Agenda(1));
agenda.add(new Agenda(2));
agenda.add(new Agenda(3));

String[] sessionID = new String[] {"1", "3"};

You can do:

List<Agenda> agendaFiltered = agenda.stream()
        .filter(agendaObj -> Arrays.binarySearch(sessionID, Integer.toString(agendaObj.getId())) >= 0)
        .collect(Collectors.toList());

Then if you run:

agendaFiltered.forEach(System.out::println);

It will print only:

Agenda{id=1}
Agenda{id=3}

edited Jun 17, 2019 at 6:12

answered Jun 7, 2019 at 8:39

Brother

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4 Comments

user11527839 Over a year ago

Thanks for the comment! My Agenda is an ArrayList. Will this example still work?

Brother Over a year ago

updated @user11527839. As you were saying array, I did it with array. Now Agenda is a List.

Brother Over a year ago

hi @user11527839 can you accept it this solves the issue, thanks.

user2637293 Over a year ago

The naming is little bit confusing. .filter() runs on objects, not filters. List<Agenda> agendaFiltered = agenda.stream() .filter(agendaObj -> sessionIdsArray.contains(agendaObj.id)) .collect(Collectors.toList());

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