Working on array of object

Question

I have following class in which I am going to store name and position of user,

public class NameAndPosition {

    private String name = "";
    private LatLng position = null;


    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public LatLng getPosition() {
        return position;
    }
    public void setPosition(LatLng position) {
        this.position = position;
    }

}

And in my MainActivity class I have created an ArrayList of objects of class NameAndPostion,

ArrayList<NameAndPosition> LocSenders = new ArrayList<NameAndPosition>();

In somewhere in my code I want to check if LocSenders contains a user with a given name. I don't want to matter a position here. I just want to check with name in LocSenders ArrayList.

e.g. I have specified a name John then I want to retrieve those objects in ArrayList which has name John.

How to do that?

Thanks in advance.

I bet you wished Java had LINQ ;) On a serious note.. what have you tried? — Lews Therin
– Lews Therin, Commented Apr 2, 2015 at 15:28
I am trying with contains method of ArrayList class. But I am not getting what I want — Gaurav Deshpande
– Gaurav Deshpande, Commented Apr 2, 2015 at 15:29
@user370305 I disagree. This will make all NameAndPosition instances with identical name equal to each other, no matter of their position. This is a serious limitation that might not be acceptable. — isnot2bad
– isnot2bad, Commented Apr 2, 2015 at 15:50

isnot2bad · Accepted Answer · 2015-04-02 15:38:04Z

3

Since Java 8, you can use the Stream API for things like that.

Collection<NameAndPosition> list = ...;
String name = ...;
boolean inList = list.stream().anyMatch(e -> name.equals(e.getName()));

answered Apr 2, 2015 at 15:38

isnot2bad

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2 Comments

Lews Therin Over a year ago

Plus one.. Not quite there.. but close enough :)

Lews Therin Over a year ago

@weston Absolutely nothing. It was a weak dig at LINQ vs Stream API. I haven't used Java in 2 or more years but glad to see some progress.

weston · Accepted Answer · 2015-04-02 15:39:41Z

2

You'll need to loop through them and look at each name:

public static boolean ListContainsName(List<NameAndPosition> list, String name) {
    for (NameAndPosition nandp : list)
       if (name.equals(nandp.getName()))
         return true;
    return false;
}

Usage:

if (ListContainsName(LocSenders, "John"))
  // then John is in list

Alternatively

If looking up by name is pretty common, have you considered a map:

Map<String, LatLng> sendersLocations = new HashMap<String, LatLng>();

Then looking up is easier and more efficient:

if (sendersLocations.containsKey("John"))
  // then John is in list

And getting position is just as easy:

LatLng pos = sendersLocations.get("John");

edited Apr 2, 2015 at 15:39

answered Apr 2, 2015 at 15:30

weston

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