Can't add (int, double) pair to HashMap<Integer, Double>

Question

I'm working on a Java project right now, and I have a class I've created called DistanceQueue. It's signature is given by

public class DistanceQueue<Integer> extends PriorityQueue<Integer>

In this class, there is a method

public boolean add(int v)

which adds the key-value pair (v, Double.MAX_VALUE) to a HashMap called distances that is in the class DistanceQueue. However, inside of add(int v), when I type

distances.put(v, Double.MAX_VALUE);

I get the following error:

DistanceQueue.java:98: error: no suitable method found for put(int,double)
            distances.put(v, Double.MAX_VALUE);
                     ^
    method HashMap.put(Integer,Double) is not applicable
      (actual argument int cannot be converted to Integer by method invocation conversion)
  where Integer is a type-variable:
    Integer extends Object declared in class ShortestPaths.DistanceQueue
1 error

Does anyone know why I am getting this error? I thought Java automatically converted between int and Integer for you. Is there an easy way that I can fix it?

Thanks!

Answer 1

You're using Integer as the name of a type parameter, which hides the java.lang.Integer.

public class DistanceQueue<Integer> extends PriorityQueue<Integer>
                           ^^^^^^^

You should probably just drop the type parameter:

public class DistanceQueue extends PriorityQueue<Integer>