How to apply contains function on attribute of a Java Object?

Question

I have Address class as:

public class Address{
    private String city;
    private String pincode;
    private String state;
}

I have an attribute of different object request as private List<Address> transitLocations.

How can I check if transitLocations contains an address which is having state equals to "SomeString" in one line.

PS: Please assume all getters & setters are present in code.
I don't want to override equals because Address class is used at other places too.

Possible duplicate of [ArrayList's custom Contains method](http://stackoverflow.com/questions/8322129/arraylists-custom-contains-method) — Dmitry P., Feb 08 '16 at 12:48
@DurgeshSuthar Are you trying to check whether the arraylist contains an address object with the same city, pincode and state? — user3437460, Feb 08 '16 at 13:07
@DmitryP. I don't want to override equals function. Updated question. — Durgesh Suthar, Feb 08 '16 at 13:45

score 5 · Accepted Answer · answered Feb 08 '16 at 14:14

5

_{Not being sure why solutions using filter and collect have been proposed...}

You can use a Predicate and pass it to Stream#anyMatch

public boolean containsAddressWithState(
    Collection<? extends Address> collection, String state)
{
    return collection.stream().anyMatch(a -> a.getState().equals(state));
}

answered Feb 08 '16 at 14:14

Marco13

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This is better. Thanks :) – Durgesh Suthar Feb 08 '16 at 17:22

andrucz · Answer 2 · 2016-02-08T13:52:22.943

4

public boolean containsAddressWithState(List<Address> list, String state){
    return list.stream().filter(o -> o.getState().equals(state)).findFirst().isPresent();
}

Or, if you really want to do it in one single line:

boolean containsState = transitLocations.stream().filter(o -> o.getState().equals("SomeString")).findFirst().isPresent();

edited Feb 08 '16 at 13:52

answered Feb 08 '16 at 12:48

andrucz

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score 0 · Answer 3 · answered Feb 08 '16 at 13:06

0

You can override the public boolean equals(Object o) method of Object class in Address as :

public boolean equals(Object o){
        if(o instanceof Address && ((Address)o).getSomeString().equalsIgnoreCase(this.someString)){
            return true;
        }else {
            return false;
        }
    }

then you can use List.contains(Object o) method of List to verify that element(Address obj) is present or not in the list.

answered Feb 08 '16 at 13:06

Shekhar Khairnar

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Then you hurt reusability of Address class. Equals method should verify city, pincode and state to be consistent. – andrucz Feb 08 '16 at 13:13
@andrucz it's depend on OP requirement how he wants his Address to be equal – Shekhar Khairnar Feb 08 '16 at 13:15
Yes, but it's not generally a good ideia to make equals and hashCode method based on how object will be used in a specific place. Considering that exist simple ways to do what OP wants without hurting reusability, I would avoid doing like your in answer. – andrucz Feb 08 '16 at 13:20
@ShekharKhairnar: andrucz is correct. Many other classes use Address class, and there this is not the case. – Durgesh Suthar Feb 08 '16 at 13:32
1

@Durgesh Suthar: It's totally depends on the requirement and functionality. If your requirement for the equality is specific for a particular attribute for this case only you can go ahead with andrucz solution. – Shekhar Khairnar Feb 08 '16 at 13:41

How to apply contains function on attribute of a Java Object?

3 Answers3