[java] Remove Item from ArrayList

I have an ArrayList suppose list, and it has 8 items A-H and now I want to delete 1,3,5 position Item stored in int array from the list how can I do this.

I am trying to do this with

ArrayList<String> list = new ArrayList<String>();
list.add("A");
list.add("B");
list.add("C");
list.add("D");
list.add("E");
list.add("F");
list.add("G");
list.add("H");

int i[] = {1,3,5};

for (int j = 0; j < i.length; j++) {
    list.remove(i[j]);
}

But after first item deleted positioned of array is changed and in the next iterate it deletes wrong element or give exception.

String[] mString = new String[] {"B", "D", "F"};

for (int j = 0; j < mString.length-1; j++) {
        List_Of_Array.remove(mString[j]);
}

 public void DeleteUserIMP(UserIMP useriamp) {
       synchronized (ListUserIMP) {
            if (ListUserIMP.isEmpty()) {
            System.out.println("user is empty");
        }  else {
            Iterator<UserIMP> it = ListUserIMP.iterator();
            while (it.hasNext()) {
                UserIMP user = it.next();
                if (useriamp.getMoblieNumber().equals(user.getMoblieNumber())) {
                    it.remove();
                    System.out.println("remove it");
                }
            }
            // ListUserIMP.remove(useriamp);

            System.out.println(" this user removed");
        }
        Constants.RESULT_FOR_REGISTRATION = Constants.MESSAGE_OK;
        // System.out.println("This user Deleted " + Constants.MESSAGE_OK);

    }
}

If you use "=", a replica is created for the original arraylist in the second one, but the reference is same so if you change in one list , the other one will also get modified. Use this instead of "="

        List_Of_Array1.addAll(List_Of_Array);

I assume the array i is ascend sorted, here is another solution with Iterator, it is more generic:

ArrayList<String> list = new ArrayList<String>();
list.add("A");
list.add("B");
list.add("C");
list.add("D");
list.add("E");
list.add("F");
list.add("G");
list.add("H");

int i[] = {1,3,5};

Iterator<String> itr = list.iterator();
int pos = 0;
int index = 0;
while( itr.hasNext() ){
    itr.next();
    if( pos >= i.length ){
        break;
    }
    if( i[pos] == index ){
        itr.remove();
        pos++;
    }

    index++;
}

remove(int index) method of arraylist removes the element at the specified position(index) in the list. After removing arraylist items shifts any subsequent elements to the left.

Means if a arraylist contains {20,15,30,40}

I have called the method: arraylist.remove(1)

then the data 15 will be deleted and 30 & 40 these two items will be left shifted by 1.

For this reason you have to delete higher index item of arraylist first.

So..for your given situation..the code will be..

ArrayList<String> list = new ArrayList<String>();
list.add("A");
list.add("B");
list.add("C");
list.add("D");
list.add("E");
list.add("F");
list.add("G");
list.add("H");

int i[] = {1,3,5};

for (int j = i.length-1; j >= 0; j--) {
    list.remove(i[j]);
}

As mentioned before

iterator.remove()

is maybe the only safe way to remove list items during the loop.

For deeper understanding of items removal using the iterator, try to look at this thread

Try it this way,

ArrayList<String> List_Of_Array = new ArrayList<String>();
List_Of_Array.add("A");
List_Of_Array.add("B");
List_Of_Array.add("C");
List_Of_Array.add("D");
List_Of_Array.add("E");
List_Of_Array.add("F");
List_Of_Array.add("G");
List_Of_Array.add("H");

int i[] = {5,3,1};

for (int j = 0; j < i.length; j++) {
    List_Of_Array.remove(i[j]);
}

You can remove elements from ArrayList using ListIterator,

ListIterator listIterator = List_Of_Array.listIterator();

 /* Use void remove() method of ListIterator to remove an element from List.
     It removes the last element returned by next or previous methods.
 */
listIterator.next();

//remove element returned by last next method
listIterator.remove();//remove element at 1st position
listIterator.next();
listIterator.next();
listIterator.remove();//remove element at 3rd position
listIterator.next();
listIterator.next();
listIterator.remove();//remove element at 5th position

How about this? Just give it a thought-

import java.util.ArrayList;

class Solution
{
        public static void main (String[] args){

             ArrayList<String> List_Of_Array = new ArrayList<String>();
             List_Of_Array.add("A");
             List_Of_Array.add("B");
             List_Of_Array.add("C");
             List_Of_Array.add("D");
             List_Of_Array.add("E");
             List_Of_Array.add("F");
             List_Of_Array.add("G");
             List_Of_Array.add("H");

             int i[] = {1,3,5};

             for (int j = 0; j < i.length; j++) {
                 List_Of_Array.remove(i[j]-j);
             }

             System.out.println(List_Of_Array);

        }


}

And the output was-

[A, C, E, G, H]