JAVA for循环语句的循环变量类型问题

class HalfDollars

  {
       public static void main(String [] arguments)
          { int[] denver = {1_900_000,1_700_000,1_700_000 };
            int[] philadelphia ={1_900_000,1_800_000,1_750_000};
            int[] total = new int[denver.length];
            int sum =0;
            for (int i=0,int j=2009;i<3;i++,j++)
                { total[i]=denver[i]+philadelphia[i];
                  System.out.print(j+"production:");
                  System.out.format("%,d%n",total[i]);
                  sum += total[i];
                 }

            System.out.print("Average production:");
            System.out.format("%,d%n",sum/3);
           }
   }

以上代码会报错：

class HalfDollars

  {
       public static void main(String [] arguments)
          { int[] denver = {1_900_000,1_700_000,1_700_000 };
            int[] philadelphia ={1_900_000,1_800_000,1_750_000};
            int[] total = new int[denver.length];
            int sum =0;
            for (int i=0, j=2009;i<3;i++,j++)
                { total[i]=denver[i]+philadelphia[i];
                  System.out.print(j+"production:");
                  System.out.format("%,d%n",total[i]);
                  sum += total[i];
                 }

            System.out.print("Average production:");
            System.out.format("%,d%n",sum/3);
           }
   }

以上代码正常执行

由上可知：代码的数据类型只能是byte、char 、short、int以及String这5种；并且两个循环变量for(int x,y)的类型一定要相同，并且只能声明一次类型。