Swapping Keys and values into my second HashMap.

Question

example...in python...... but looking to do similar in java.
dict1 = dict(zip(list1, list2)
dict2 = dict(zip(list2, list1) # see how the lists are swapped in this dict.

How can I swap the keys and values of my first HashMap into my second HashMap?

I've had a look in the java docs on-line, but the constructor and "putAll" only takes a whole HashMap. (as I understand).

Answer 1

rodwynnejones you were on the right track there with keySet() . Here is an example.

https://code.sololearn.com/cb4GFoQCZkdt/?ref=app

Answer 2

@Avinesh
Thank you for responding....that's what I ended up doing.
...but now I'm thinking about it.......maybe I can do a for-each loop using the myHashMap.keySet() and do it that way........but that's for tomorrow.
Thanks anyway.

Answer 3

This is what I ended up with.....might be of interest to another beginner:-
HashMap<Character, Integer> HashMapOne = new HashMap<Character, Integer>();
HashMap<Integer, Character> HashMapTwo = new HashMap<Integer, Character>();

HashMapOne.put('a', 1);
HashMapOne.put('b', 2);
HashMapOne.put('c', 3);
// etc....

for(Character x: HashMapOne.keySet())
HashMapTwo.put(HashMapOne.get(x), x);

Answer 4

I doubt if you can do that using a single line function in java. It has to be completely manually entered.

Answer 5

Only thing to be noted, is that hashmap has unique keys but not necessary unique values.
So if you swap the keys/values when some keys point to the same value, you might lose some data. Of course not the case with this particular example.