java – fix the randomOperator method with these directions: you need a random object. You could either create it inside the method or create a static object

fix the randomOperator method with these directions: you need a random object. You could either create it inside the method or create a static object.
This is the code so far:

  public static Binop randomOperator(Node l, Node r) {
   int operator = random.nextInt(4);
   switch (operator) {
   case 0:
   return new Plus(l, r);
   case 1:
   return new Subtract(l, r);
   case 2:
   return new Multiply(l, r);
   case 3:
   return new Divide(l, r);
   default:
   return null;
    }
  }