How to find index position of an element in a list when contains returns true

How to find index position of an element in a list when contains returns true

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I've got a List of HashMap so I'm using List.contains to find out if the list contains a specified HashMap. In case it does, I want to fetch that element from the list, so How do I find out index position of where the element is?

    List benefit = new ArrayList();
    HashMap map = new HashMap();
    map.put("one", "1");
    benefit.add(map);
    HashMap map4 = new HashMap();
    map4.put("one", "1");

    System.out.println("size: " + benefit.size());
    System.out.println("does it contain orig: " + benefit.contains(map));
    System.out.println("does it contain new: " + benefit.contains(map4));

    if (benefit.contains(map4))
        //how to get index position where map4 was found in benefit list?

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What's wrong with:

benefit.indexOf(map4)

? It either returns an index or -1 if the items is not found.

BTW I strongly recommend wrapping the map in some object and use generics if possible.

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indexOf(object)

get(index)

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Here is an example:

List<String> names;
names.add("toto");
names.add("Lala");
names.add("papa");
int index = names.indexOf("papa"); // index = 2

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Use List.indexOf(). This will give you the first match when there are multiple duplicates.

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List#indexOf

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int indexOf(Object o) This method returns the index in this list of the first occurrence of the specified element, or -1 if this list does not contain this element.

참고URL : https://stackoverflow.com/questions/9008532/how-to-find-index-position-of-an-element-in-a-list-when-contains-returns-true