Type mismatch: cannot convert from element type Object to int

Question

I'm getting the following error on the line where it says ht.keySet() :

Type mismatch: cannot convert from element type Object to int

ht is a LinkedHashMap .

for (int key : ht.keySet())
{
    if(ht.get(key).size() == 0)
    {
         System.out.println("There is no errors in " + key) ;
    }
    else
    {
        System.out.println("ERROR: there are unexpected errors in " + key);
    }
}

Answer 1

You need to use Java generics .

Declare ht as a LinkedHashMap<Integer, Foo> where Foo is whatever data type you expect to be returned by ht.get() . Using the Map interface would be even better:

LinkedHashMap<Integer, Foo> ht = new LinkedHashMap<Integer, Foo>();
// or preferably
Map<Integer, Foo> ht = new LinkedHashMap<Integer, Foo>();

Answer 2

ht is a LinkedHashMap , if it contains only Integer s, you should declare it as LinkedHashMap<Integer,Object> .

If it will be declared as LinkedHashMap<Integer,Object> , the unboxing to an int will be done automatically.

(*) even better if you declare it as LinkedHashMap<Integer,[actual-object-type]>

Answer 3

It must be: for (Integer key : ht.keySet())...

LinkedHashMap<K, V> where K and V are Objects, not primitiv (int, short ...)

Answer 4

Use Integer instead of int and it will probably work. The keys in the LinkedHashMap must be objects, not primitive types.