Question

Ok I’ve been searching for this problem for a while.
I keep getting an error that I can’t instantiate abstractSet.
It keeps asking for a generic. I add the generic but still no dice.

import java.util.AbstractSet;
import java.util.Set;
public class UnorderedTree{

private Object root;
private Set subtrees; //Switched to AbstractSet
private int size;

public UnorderedTree(Object root){
     this(root);
     subtrees = new AbstractSet(); //ERROR HERE WITH <Object>
     size=1;
   }
}

Any pointers would help

Answer 1

As its name suggested, AbstractSet is abstract, you can not instantiate it. as its javadoc said:

This class provides a skeletal implementation of the Set interface to minimize the effort required to implement this interface.

You should use some concrete set like HashSet.