Updating elements in an ArrayList in Java?

Question

I have the following class:

public class Profile{
    String name, age, location;
}

Say that I then have the following code:

ArrayList<Profile> profiles = somePopulatedArrayList;
Profile profile = profiles.get(1);
profile.name = "New name here";

My question is when I have the above, is the .name of the object in the ArrayList getting updated, or am I creating a completely new object here and only changing the .name of that object while the Profile object stored in the ArrayList still has the old name?

I'm trying to edit properties of objects in the ArrayList and I'm wondering if the above approach is correct or not?

It's not a good practice to access class fields that way. You should declare them as private fields and use getters/setters instead. — Amin Abu-Taleb
– Amin Abu-Taleb, Commented Aug 26, 2013 at 15:46
There's no 'object' in the ArrayList, that's what you need to learn from this question. The list contains references (an address) that points to some object in memory. — Fernando
– Fernando, Commented Aug 26, 2013 at 15:48

Kent · Accepted Answer · 2013-08-26 15:42:31Z

4

No new object was created. You've updated the object in the list, that is, the object in the list will have "New name here" as name.

In fact this you could test and see with a debugger.

answered Aug 26, 2013 at 15:42

Kent

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Algorithmist · Accepted Answer · 2013-08-26 15:45:54Z

2

No New Object is Created, you are modifying the existing value.

In fact this is not a good practice,you should allow access to your class variables directly, make them as private and provide setter/getter methods for the same.

public class Profile {
    private String name, age, location;

    public String getName() {
        return name;
    }

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

    public String getAge() {
        return age;
    }

    public void setAge(String age) {
        this.age = age;
    }

    public String getLocation() {
        return location;
    }

    public void setLocation(String location) {
        this.location = location;
    }

}

answered Aug 26, 2013 at 15:45

Algorithmist

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chrylis -cautiouslyoptimistic- · Accepted Answer · 2013-08-26 15:43:22Z

2

In Java, all variables that are object types hold references to objects. When you call get on a collection, it returns a reference to the object that's inside it, so if you then proceed to modify that object, the changes will be seen by anyone else looking at the same object.

answered Aug 26, 2013 at 15:43

chrylis -cautiouslyoptimistic-

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