Incompatible types while using weighted randomness in java

I tried to implement Weighted Randomness in Java

so I found following codes

1. RandomCollection Class

2. RandomTopic Class

   public class RandomCollection<E> {
     private final NavigableMap<Double, E> map = new TreeMap<Double, E>();
     private final Random random;
     private double total = 0;
   
   public RandomCollection() {
   this(new Random());
   }
   
   public RandomCollection(Random random) {
   this.random = random;
   }
   
   public RandomCollection<E> add(double weight, E result) {
   if (weight <= 0) return this;
   total += weight;
   map.put(total, result);
   return this;
   }
   
   public E next() {
   double value = random.nextDouble() * total;
   return map.higherEntry(value).getValue();
   }
   
   
   }
   
   
   public class RandomTopic {
   
   RandomCollection<String> rc = new RandomCollection<>().add(40, "dog").add(35, "cat").add(25, "horse");
   
   }
   
   

However, the IDE shows the following error at

"RandomCollection String rc"

Incompatible types.

Required: RandomCollection java.lang.String

Found: RandomCollection java.lang.Object

How can I solve the problem? please help