New to Java

Hello,

I need to sort an ArrayList of rational numbers, using methods from the Collections Framework classes to sort the elements into increasing order. I am getting an error message when compiling my code, which is 'cannot find symbol - method sort(java.util.List<Rational>)'. Can someone point me in the right direction?

Thanks for any help

Here's the code:

public interface Comparable<T>
{
    public int compareTo(T o);
}

import java.util.*;

public class Rational implements Comparable<Rational>
{
        
    private int numerator;
    private int denominator;
    
     // Constructor
    public Rational(int n, int d) 
    { 
        numerator = n; 
        denominator = d; 
    }
    
    public  static void main(String[] args)
    {
       List<Rational> rationals = new ArrayList<Rational>();
       rationals.add(new Rational(3,1));   
       rationals.add(new Rational(22,7));
       rationals.add(new Rational(333,106));
       rationals.add(new Rational(355,113));
       rationals.add(new Rational(103993,33102));
       rationals.add(new Rational(104348,33215));
       rationals.add(new Rational(208341,66317));
       System.out.println(rationals);
       Collections.sort(rationals);
       System.out.println(rationals);
   
   }  
      
   public int compareTo(Rational o) 
   {
        Rational r = (Rational) o;
        int result = numerator*r.denominator - r.numerator*denominator;
        if (result>0) return 1;
            else if (result < 0) return -1; 
                else return 0;
   }
   
   public boolean equals(Object o) 
   { 
        return (compareTo(o)==0); 
   }
    
   public String toString()
   { 
        return numerator+"/"+denominator; 
   }
   
   
}