Get One Element From ArrayList

Question

I have a custom object defined here:

public class ContactObject {

    public String contactName;
    public String contactNo;
    public String image;
    public boolean selected;

    public String getName() {
        return contactName;
    }

    public void setName(String contactName) {
        this.contactName = contactName;
    }

    public String getNumber() {
        return contactNo;
    }

    public void setNumber(String contactNo) {
        this.contactNo = contactNo;
    }

    public String getImage() {
        return image;
    }

    public void setImage(String image) {
        this.image = image;
    }

    public boolean isSelected() {
        return selected;
    }

    public void setSelected(boolean selected) {
        this.selected = selected;
    }

}

And I have populated an ArrayList of this custom object (binderContacts) but now I want to convert this to a normal ArrayList with a list of all the contactNo's in my array list. Can someone help here?

public class ContactsListClass {

    public static final ArrayList<ContactObject> phoneList = new ArrayList<ContactObject>();
    public static final ArrayList<ContactObject> binderContacts = new ArrayList<ContactObject>();
}

Your title doesn't make much sense. ArrayList which stores elements of some type is still ArrayList. Please correct it to better describe what you want to achieve. — Pshemo, Jan 03 '16 at 20:24
Also fields in ContactObject class should most probably be private, not public. — Pshemo, Jan 03 '16 at 20:25
Another thing is that you should prefer to [program on interfaces](http://stackoverflow.com/questions/383947/what-does-it-mean-to-program-to-an-interface) rather then its specific implementation. So your `phoneList` and `binderContacts` should be of type `List`, not `ArrayList`. This will give you more flexibility in case you would want to use other list than ArrayList. — Pshemo, Jan 03 '16 at 20:29
I edited the title - this is probably why I can't find the answer (because I am confused about arraylists/objects in general at the moment). What I want to do is take from the ArrayList binderContacts and convert it to an ArrayList with just phone numbers — Riley MacDonald, Jan 03 '16 at 20:31
Create empty ArrayList, iterate over your already filled ArrayList and for each ContactObject read its contactNo and add it to that new ArrayList. — Pshemo, Jan 03 '16 at 20:37

Rudi Angela · Answer 1 · 2016-01-03T20:33:41.123

0

Assuming you're using Java 8:

ArrayList<String> contactNos = binderContacts.stream().map(contact -> contact.getNumber()).collect(Collectors.toList());

edited Jan 03 '16 at 20:33

answered Jan 03 '16 at 20:27

Rudi Angela

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`binderContacts.stream().map(ContactObject::getNumber).collect(Collectors.toList())` – samczsun Jan 03 '16 at 20:29
`map(contact -> contact.getNumber())` returns `Stream` not `List`. – Pshemo Jan 03 '16 at 20:30
1

Hi thanks for your help, however I am developing an Android app and therefore am using Java 7 – Riley MacDonald Jan 03 '16 at 20:34

score 0 · Answer 2 · answered Jan 03 '16 at 23:46

0

List<String> contactNos = new ArrayList<String>();
for (ContactObject o : phoneList) {
    contactNos.add(o.getNumber());
}

answered Jan 03 '16 at 23:46

TomaszRykala

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Get One Element From ArrayList

2 Answers2