How to reposition keys by Number Order in Java Map?

I'm trying to remove a particular key from Map and reposition all keys index wise. For example: My map is like Map<Integer,String>

0,"A"
1,"B"
2,"C"
3,"D"

if i remove key 1 then output should be

0,"A"
1,"C"
2,"D"

How do i keep keys in index wise (0 to size-1) and assign next value to previous key after remove?

This is required because before insertion in map i need to check whether key exists or not. This scenario required for my recycler view adapter to hold unique positions to avoid reloading of items if exists in map

In your situation, if u want the index to be in that behavior. Map is not the answer. use List - can use ArrayList[insertion is often] or LinkedList[fast when reading].

Sample:

List<String> items = new ArrayList<>();

items.add("A");
items.add("B");
items.add("C");
items.add("D");

So if you remove index 1 or B;

items.remove(1);

The index of C will automatically be 1. Just like you wanted above.

Maps inherently have no order. There is no way to change the keys without taking all the values out of the Map and reinserting them with new keys.

It sounds like you may be better off using a List instead of a Map.

ArrayList<String> strings = new ArrayList(Arrays.asList("A", "B", "C"));
// 0 => "A", 1 => "B", 2 => "C"
strings.remove(1);
// 0 => "A", 1 => "C"

You can't order the keys on deletion by updating key values. In MAP only way to update keys is removing the key and and re-insert it with new value. That is tricky and expensive. You can go with ArrayList for the desired result as suggested.

The TreeMap<K,V> in the jdk java.util package can meet your needs. Whatever key you delete , the sort will never change.

If you want to define yourself sort method, just use its custom comparator to over-write construction method TreeMap(Comparator<? super K> comparator) to achieve key sorting.

public static void main(String[] args) {  
    Map<Integer, String> map = new TreeMap<Integer, String>();  
    map.put(0, "A");
    map.put(1, "B");
    map.put(2, "C");
    map.put(3, "D");
    // whatever key you delete , the sort will not change...
    for (Map.Entry<Integer, String> entry : resultMap.entrySet()) {  
        System.out.println(entry.getKey() + " " + entry.getValue());  
    }  
}  

you choose a very bad way to implement this in adapter
but you can solve it with below code:

 final Map<Integer, String> myStupidMap = new HashMap<>();
    myStupidMap.put(1, "A");
    myStupidMap.put(2, "B");
    myStupidMap.put(3, "C");
    myStupidMap.put(4, "D");

    final int[] count = {0};
    if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.N) {
        myStupidMap.forEach(new BiConsumer<Integer, String>() {
            @Override
            public void accept(Integer integer, String s) {
                if (count[0] == 1){
                    myStupidMap.remove(integer);
                }
                count[0]++;
            }
        });
    }

i hope useful for you But my suggestion is not to use the map.