通配符测试程序。

import java.util.ArrayList;


public class Main 

{// 来自 nowjava

   public static void main(String[] args) 

   {


      Integer[] integers = {1, 2, 3, 4, 5};

      ArrayList<Integer> integerList = new ArrayList<>();


      // insert elements in integerList

      for (Integer element : integers)

         integerList.add(element);


      System.out.printf("integerList contains: %s%n", integerList);

      System.out.printf("Total of the elements in integerList: %.0f%n%n",

         sum(integerList));


      // create, initialize and output ArrayList of Doubles, then 

      // display total of the elements 

      Double[] doubles = {1.1, 3.3, 5.5};/** from 时代Java**/

      ArrayList<Double> doubleList = new ArrayList<>();


      // insert elements in doubleList

      for (Double element : doubles)

         doubleList.add(element);


      System.out.printf("doubleList contains: %s%n", doubleList);

      System.out.printf("Total of the elements in doubleList: %.1f%n%n", 

         sum(doubleList));


      // create, initialize and output ArrayList of Numbers containing 

      // both Integers and Doubles, then display total of the elements 

      Number[] numbers = {1, 2.4, 3, 4.1}; // Integers and Doubles

      ArrayList<Number> numberList = new ArrayList<>();


      // insert elements in numberList

      for (Number element : numbers)

         numberList.add(element);


      System.out.printf("numberList contains: %s%n", numberList);

      System.out.printf("Total of the elements in numberList: %.1f%n", 

         sum(numberList));

   } 


   // total the elements; using a wildcard in the ArrayList parameter

   public