How to get element position from Java Map

java

Solution

Though a bit late to answer. But the option is to use `LinkedHashMap`: this map preserves the order according to insertion of elements, as everyone has suggested. However, As a warning, it has a constructor `LinkedHashMap(int initialCapacity, float loadFactor, boolean accessOrder)` which will create a linked hash map whose order of iteration is the order in which its entries were last `accessed`. Don't use this constructor for this case.

However, if I needed such functionality, i would extend it and implement my necessary function to re-use them in OOP way.

class MyLinkedMap<K, V> extends LinkedHashMap<K, V>
{

    public V getValue(int i)
    {

       Map.Entry<K, V>entry = this.getEntry(i);
       if(entry == null) return null;

       return entry.getValue();
    }

    public Map.Entry<K, V> getEntry(int i)
    {
        // check if negetive index provided
        Set<Map.Entry<K,V>>entries = entrySet();
        int j = 0;

        for(Map.Entry<K, V>entry : entries)
            if(j++ == i)return entry;

        return null;

    }

}

Now i can instantiate it and can get a entry and value either way i want:

MyLinkedMap<String, Integer>map = new MyLinkedMap<>();
map.put("a first", 1);
map.put("a second", 2);
map.put("a third", 3);

System.out.println(map.getValue(2));
System.out.println(map.getEntry(1)); 

Output:

3
a second=2

Problem

Original source

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