TreeMap with generic key types

Question

I am using a TreeMap to add entries that are of type <Integer,Long>. However, I may have cases where the entries will be of type <Long, Long> and I would like to construct a TreeMap that can handle both cases. So far, I have

public class myClass {
    public TreeMap<Integer, String> myClass(String fileToRead) {
        ....
        TreeMap<Integer, String> map = new TreeMap<>();    
        map.put(Integer, String); //this is a for loop that iterates through input list
    }
    return map
} 

How do I add a generic key K that can be Integer or Long?

Edit: I would like to include other types, such as BigInteger

Answer 1

Sounds like you may want something like

public class MyClass<T extends Number> {
  public TreeMap<T, String> myClass(String fileToRead) {
  ...
}

BigInteger too would fill the Number bill.

But to avoid the complication with the generics, I would actually suggest to always use Long as the key type or even BigInteger, except you have strong requirements not to do so. Depending on the JVM you use (64bit) an Integer object may not even use less space than a Long object.