Remove a specific element from an Arraylist in Java?

Question

I have an Arraylist with (String-)Arrays in it. Now I want to be able to delete a specific element from the Arraylist.

Here is an example arraylist:

0:  [Name, , , ]
1:  [Telefon, \(\d+\) \d+, DAFAE8, FF6262]
2:  [E-Mail, ^[a-zA-Z0-9]+(?:(\.|_)[A-Za-z0-9!#$%&'*+/=?^`{|}~-]+)*@(?!([a-zA-Z0-9]*\.[a-zA-Z0-9]*\.[a-zA-Z0-9]*\.))(?:[A-Za-z0-9](?:[a-zA-Z0-9-]*[A-Za-z0-9])?\.)+[a-zA-Z0-9](?:[a-zA-Z0-9-]*[a-zA-Z0-9])?$, DAFAE8, FF6262]
3:  [Company, , , ]
4:  [Test, , , ]
5:  [Test2, , , ]
6:  [Test3, , , ]

Now I want to delete the 5th element (the array which includes Test2). How do I accomplish that?

I already tried the following things:

public static List<String[]> removeSpecificElements(List<String[]> list, int i){
    list.remove(new Integer(i));
    return list;
}

This one doesn't throw any kind of Exception, but doesn't work either.

public static List<String[]> removeSpecificElements(List<String[]> list, int i){
    list.remove(i);
    return list;
}

This one throws ArrayIndexOutOfBounds.

public static List<String[]> removeSpecificElements(List<String[]> list, int i){
    Iterator<String[]> itr = list.iterator();
    itr.next();
    for (int x = 0; x < i; x++){
        itr.next();
        System.out.println(itr);
    }
    itr.remove();
    return list;
}

And this one always removes the first element.

Could you please help me?

There are numerous questions about how to delete elements from a list on this site. Did you bother searching for them first? — Raedwald
– Raedwald, Commented Feb 25, 2016 at 9:28

Peter Lawrey · Accepted Answer · 2016-02-25 09:30:19Z

4

Now I want to delete the 5th element (the array which includes Test2). How do I accomplish that?

You need to use

list.remove(i); // where i = 5 - 1, as the first element is 0.

if you do

list.remove(new Integer(i));

it will look for the object you just created, which doesn't exist in the list, so as you say it does nothing.

In short, don't confuse int for Integer as these are different types.

Ideally, the API would have a different method like removeAt(int) to remove this potential source of confusion, but it's too late to change it now.

When would this work? Consider the following.

List<Integer> ints = new ArrayList<>();
ints.add(4);

List<MyType> list = (List) ints; // it works but don't do this.
boolean wasRemoved = list.remove(new Integer(4)); // true!!

edited Feb 25, 2016 at 9:30

answered Feb 25, 2016 at 9:14

Peter Lawrey

535k83 gold badges770 silver badges1.2k bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

Andy Turner Over a year ago

I would maybe say that new Integer(i) can't exist in the list (rather than simply doesn't), because of generics.

Peter Lawrey Over a year ago

@AndyTurner actually it could exist if you had used generics incorrectly.

WorkHardDieSoon Over a year ago

Thanks, this made me realize my mistake. (which basically was that I first select an visual element, remove it and then try to remove the data behind the element with the now non-existant selection...)

Peter Lawrey Over a year ago

@WorkHardDieSoon unfortunately its a reasonably common mistake to make.

Boris Pavlović · Accepted Answer · 2016-02-25 09:13:35Z

3

java.util.List#remove(int) should work, just don't forget that lists are zero indexed, i.e. 5th element is removed calling list.remove(4)

answered Feb 25, 2016 at 9:13

Boris Pavlović

64.9k29 gold badges127 silver badges150 bronze badges

Collectives™ on Stack Overflow

Remove a specific element from an Arraylist in Java?

2 Answers 2

4 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

4 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related