Foreach-怎么了？

Question

下面的两个示例都应该对数组元素求和，但是这没有发生。在第一个中，我得到了总和，但是在第二个中，我得到了数组中的值。怎么了？

• Java-

第一个：

< double [] arr = {1.0,2.0,3.0,4.0,5.0};
    double sum = 0.0;

    for (int i = 0 ; i<arr.length; i++) {
            sum += arr[i];              

        System.out.println ("arr sum is :" + sum); }
>

第二个：

<  double [] arr = {1.0,2.0,3.0,4.0,5.0};
    double sum = 0.0;

    for (double d : arr) {
    sum += d;

    System.out.println (d);  }

>

第一个结果是：

arr sum is :1.0
arr sum is :3.0
arr sum is :6.0
arr sum is :10.0
arr sum is :15.0

但第二个返回：

1.0
2.0
3.0
4.0
5.0

Answer 1

在第二个示例中，您正在打印d，而应该打印sum变量：

double [] arr = {1.0,2.0,3.0,4.0,5.0};
double sum = 0.0;

for (double d : arr) {
    sum += d;
    System.out.println(sum);  // fixed
}

Answer 2

对于第二个，您正在打印相加而不是和的数字。如果您将代码更改为此，它将起作用：

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