How can i remove an element in a string list in java?

Question

As u can see i wanna delete or remove the ingrediant which equals my ingredientid from my SplitedIgrediants list, i've tried with remove or delete but it's appear an error. So how can i do to delete this ingredient elemant please from my list in JAVA.

        String ingredientid = request.getParameter("id");
        DbHandler dbsplt = new DbHandler();
        for (String ingrediant : SplitedIngrediants) {
            if (ingrediant.equals(ingredientid)) {
                //HERE REMOVE THE ingredient from SplitedIngrediants list
            }

how are we to know? we don't even know the type of SplitedIngrediants — Stultuske
– Stultuske, Commented Apr 5, 2018 at 9:06
What is SplitedIngrediants. Best we see the other parts of the code — someguy76
– someguy76, Commented Apr 5, 2018 at 9:08
@Stultuske look at the code closely, it's a for each loop, so since it's wrote in the title and the sub element is of type String, i guess SplitedIngrediants is a List of type String aswell. — N.K
– N.K, Commented Apr 5, 2018 at 9:09
@xoxel you have no idea how many people think String[] myList is a 'list of Strings' — Stultuske
– Stultuske, Commented Apr 5, 2018 at 9:10

Arnaud Denoyelle · Accepted Answer · 2018-04-05 09:22:26Z

1

You cannot remove elements from a Collection while iterating on it (you will get some ConcurrentModificationException) except if you manually declare the iterator and use iterator.remove().

Example :

List<Integer> list = new ArrayList<Integer>();

list.add(3);
list.add(4);
list.add(5);

Iterator<Integer> it = list.iterator();
Integer current;
while (it.hasNext()) {
    current = it.next();
    if(current.equals(4)) {
        it.remove();
    }
}

Ouput :

[3, 5]

The reason behind that is that the "foreach" construction internally creates an iterator. The aim of the iterator is to ensure that each element of the iterable is visited exactly once. So if you add/remove elements from the iterable without using the iterator methods, the iterator can no longer fulfil its task.

2nd option : while iterating on the list, make a list of the items to delete and delete them after iterating.

edited Apr 5, 2018 at 9:22

answered Apr 5, 2018 at 9:10

Arnaud Denoyelle

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Comments

Amitabha Roy · Accepted Answer · 2018-04-05 09:36:19Z

0

Try this:

String ingredientid = request.getParameter("id");
SplitedIngrediants.removeAll(Collections.singleton(ingredientid));

Example code:

public static void main(String args[]) {
        List<String> l = new ArrayList<String>();
        l.add("first");
        l.add("first");
        l.add("second");

        String ingredientid = "first";

        l.removeAll(Collections.singleton(ingredientid));

        System.out.println(l);
    }

With SplitedIngrediants is a String array try this:

public static void main(String args[]) {
    String[] SplitedIngrediants = new String[] { "first", "first", "second" };

    String ingredientid = "first";

    List<String> NewSplitedIngrediants = new ArrayList<>();
    for (String ingrediant : SplitedIngrediants) {
        if (!ingrediant.equals(ingredientid)) {
            NewSplitedIngrediants.add(ingrediant);
        }
    }
    SplitedIngrediants = new String[NewSplitedIngrediants.size()];
    SplitedIngrediants = NewSplitedIngrediants.toArray(SplitedIngrediants);
    for (String ingrediant : SplitedIngrediants) {
        System.out.println(ingrediant);
    }

}

edited Apr 5, 2018 at 9:36

answered Apr 5, 2018 at 9:16

Amitabha Roy

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7 Comments

Amine Chouar Over a year ago

What Collections for and singleton for ?

Amine Chouar Over a year ago

It's said that cannot find symobol of removeAll

Amitabha Roy Over a year ago

SplitedIngrediants is a java.util.List? If yes then there must be removeAll() method.

Amine Chouar Over a year ago

No i declare like this String[] SplitedIngrediants a table of strings

Amine Chouar Over a year ago

Because what i do actually is that i split a string with "," and add it to my string table

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