Storing and Retrieving ArrayList values from hashmap

Question

I have a hashmap of the following type

HashMap> map=new HashMap>();    
<         


        

Answer 1

Iterator it = map.entrySet().iterator();
while (it.hasNext()) {
     Map.Entry pairs = (Map.Entry)it.next();

     if(pairs.getKey().equals("mango"))
     {
        map.put(pairs.getKey(), pairs.getValue().add(18));
     }

     else if(!map.containsKey("mango"))
     {
        List ints = new ArrayList();
        ints.add(18);
        map.put("mango",ints);
     }

     it.remove(); // avoids a ConcurrentModificationException
}

EDIT: So inside the while try this:

map.put(pairs.getKey(), pairs.getValue().add(number))

You are getting the error because you are trying to put an integer to the values, whereas it is expected an ArrayList.

EDIT 2: Then put the following inside your while loop:

if(pairs.getKey().equals("mango"))
{
    map.put(pairs.getKey(), pairs.getValue().add(18));
}

else if(!map.containsKey("mango"))
{
     List ints = new ArrayList();
     ints.add(18);
     map.put("mango",ints);
 }

EDIT 3: By reading your requirements, I come to think you may not need a loop. You may want to only check if the map contains the key mango, and if it does add 18, else create a new entry in the map with key mango and value 18.

So all you may need is the following, without the loop:

if(map.containsKey("mango"))
{
    map.put("mango", map.get("mango).add(18));
}

else
{
    List ints = new ArrayList();
    ints.add(18);
    map.put("mango", ints);
}