How to add element at specific index/position in LinkedHashMap?

Question

I have an ordered LinkedHashMap and i want to add element at specific index , say at first place or last place in the map. How can i add element in LinkedHashMap at an specific position?

Even if I could add an element to FIRST or LAST position in LinkedHashMap would help!

Answer 1

You could do this element adding to 1. or last place:

Adding to last place ► You just need to remove the previous entry from the map like this:

map.remove(key); map.put(key,value); 

Adding to first place ► It's a bit more complicated, you need to clone the map, clear it, put the 1. value to it, and put the new map to it, like this:

I'm using maps with String keys and Group (my custom class) values:

LinkedHashMap<String, Group> newMap=(LinkedHashMap<String, Group>) map.clone(); map.clear(); map.put(key, value); map.putAll(newMap); 

As you see, with these methods you can add unlimited amount of things to the begin and to the end of the map.

Answer 2

You can not change the order. It is insert-order (by default) or access-order with this constructor:

public LinkedHashMap(int initialCapacity, float loadFactor, boolean accessOrder)

• Constructs an empty LinkedHashMap instance with the specified initial capacity, load factor and ordering mode.

• Parameters: initialCapacity - the initial capacity loadFactor - the load factor accessOrder - the ordering mode - true for access-order, false for insertion-order

• Throws: IllegalArgumentException - if the initial capacity is negative or the load factor is nonpositive

See: LinkedHashMap