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Override indexOf in LinkedList to check for identity, not equality





I have a List (actually a LinkedList) and I add Items to it which implement the equals-method.

The problem is that I add items that are equal, but not identical (like two initialized objects). Now, when I want to get the index of the item I added second, I get, of course, the element of the first item, because indexOf searches for equality and not identity.

I tried to create my own subclass of LinkedList and overwrite the indexOf-method, but this is not possible, because I don't have access to neither the subclass Node nor the Node-Element first.

Here is an example:

public class ExampleObject {

  int number;

  public ExampleObject(){
    number = 0;

  public boolean equals(Object obj) {
    if (this == obj) return true;
    if (obj == null) return false;
    if (getClass() != obj.getClass()) return false;
    ExampleObject other = (ExampleObject) obj;
    if (number != other.number) return false;
    return true;

  public static void main(String[] args) {
    LinkedList<ExampleObject> list = new LinkedList<ExampleObject>();

    ExampleObject one = new ExampleObject();
    ExampleObject two = new ExampleObject();


    System.out.println(list.indexOf(one)); // '0' as expected
    System.out.println(list.indexOf(two)); // '0', but I want to get '1'


My intention: I need a list of objects, where I want to store initialized objects and edit them later.

like image 828
MyPasswordIsLasercats Avatar asked Mar 24 '23 05:03


1 Answers

Do the iteration yourself, indexOf is just a helper method:

static int indexOfById(List<?> list, Object searchedObject) {
  int i = 0;
  for (Object o : list) {
    if (o == searchedObject) return i;
  return -1;
like image 78
Marko Topolnik Avatar answered Apr 06 '23 07:04

Marko Topolnik