// Fig. 20.10: TotalNumbers.java
// Totaling the numbers in a List<Number>.
import java.util.ArrayList;
import java.util.List;

public class TotalNumbers {
   public static void main(String[] args) {
      // create, initialize and output List of Numbers containing 
      // both Integers and Doubles, then display total of the elements 
      Number[] numbers = {1, 2.4, 3, 4.1}; // Integers and Doubles
      List<Number> numberList = new ArrayList<>();           

      for (Number element : numbers) {
         numberList.add(element); // place each number in numberList
      }

      System.out.printf("numberList contains: %s%n", numberList);
      System.out.printf("Total of the elements in numberList: %.1f%n", 
         sum(numberList));
   }

   // calculate total of List elements
   public static double sum(List<Number> list) {
      double total = 0; // initialize total

      // calculate sum
      for (Number element : list) {     
         total += element.doubleValue();
      }                                 

      return total;
   }
}

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