(Solved) : Package Dsinterfaces Import Dsstudentstoken Public Interface List Public Boolean Add Int I Q37018423 . . . .

package ds.interfaces;

import ds.students.Token;
public interface List {
   public boolean add(int index, Token obj);
   public boolean contains(Token obj);
   public boolean remove(Token obj);
   public Token remove(int index);
   public Token get(int index);
   public int indexOf(Token token);
   public boolean add(Token obj);
   public boolean isEmpty();  
   public int size();
   public String toString();   
   public boolean equals(Object obj);
   public int hashCode();
}

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package ds.interfaces;

import ds.students.DSList;
import ds.students.Token;

public abstract class Stack {
   protected DSList list;
   public abstract Token peek();
   public abstract Token pop();
   public abstract Token push(Token obj);
   public abstract String toString();
   public abstract boolean isEmpty();
   public abstract int size();

}

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package ds.interfaces;

import ds.students.DSList;
import ds.students.Token;

public abstract class Stack {
   protected DSList