JDK5.0新特性系列---2.新的for循环

 

import java.util.ArrayList;

import java.util.List;

 

/**

 * 新的for循环,格式为for(type x:type y)

 * 表示遍历数组或集合y的元素,把元素值赋给x

 */

public class ForEach {

       /**对整数数组求和*/

       public static long getSum(int[] nums) throws Exception{

              if(nums == null)

                     throw new Exception("错误的参数输入,不能为null!");

              long sum = 0;

              //依次取得nums元素的值并累加

              for(int x : nums){

                     sum += x;

              }

              return sum;

       }

       /**对整数列表求和*/

       public  static long getSum(List<Integer> nums) throws Exception{

              if(nums == null)

                     throw new Exception("错误的参数输入,不能为null!");

              long sum = 0;

              //可以与遍历数组一样的方式遍历列表

              for(int x:nums){

                     sum += x;

              }

              return sum;

       }

       /**求多维数组的平均值*/

       public static int getAvg(int[][] nums) throws Exception{

              if(nums == null)

                     throw new Exception("错误的参数输入,不能为null!");

              long sum = 0;

              long size = 0;

              //对于二维数组,每个数组元素都是一维数组

              for(int[] x : nums){

                     //一维数组中的元素才是数字

                     for(int y : x){

                            sum += y;

                            size ++;

                     }

              }

              return (int)(sum/size);

       }

      

       public static void main(String[] args)throws Exception{

              int[] nums = {456,23,-739,163,390};

              List<Integer> list_I = new ArrayList<Integer>();

              for(int i = 0; i < 5; i++){

                     list_I.add(nums[i]);

              }

              System.out.println(getSum(nums));

              System.out.println(getSum(list_I));

              int[][] numss = {{1,2,3},{4,5,6},{7,8,9,10}};

              System.out.println(getAvg(numss));

       }

}