对于循环执行，增加混淆 [英] For loop execution, increment confusion

问题描述

我不明白为什么 i in fillArray 方法最终等于 10 即使数组分数仅满足索引9 。

I don't get it why i in fillArray method ends up being equal to 10 even though the array score is filled only up to index 9.

根据我的理解 i 必须小于 10 ，那么它最终如何最终 10 ，它应该增加。

As per my understanding i has to be smaller than 10,so how can it end up being 10 at the end, it should have incremented.

我尝试了另一个循环来测试for循环如果条件为真，for循环执行增量。

I tried another loop to test if for loop executes incrementation at the end if condition is true.

In测试循环 i 最终只有10才有意义，但两个for循环相矛盾。

In test loop i ends up being only 10 which makes sense but the two for loop contradict.

public class GoldScores {
        public static final int MAX_NUMBER_SCORES = 10;
        public static void main(String[] args) {
            double[] score = new double[MAX_NUMBER_SCORES];
            int numberUsed = 0;

            System.out.println("This program reads gold scores and shows");
            System.out.println("how much each differs from the average.");
            System.out.println("Enter gold scores:");
            //numberUsed = fillArray(score);
        //  showdifference(score,numberUsed);
             for(int i=1; i<11; i++){                   //Test loop
                 System.out.println("Count is: " + i);
            }
        }
        private static void showdifference(double[] score, int numberUsed) {
            // TODO Auto-generated method stub

        }
        public static int fillArray(double[] a){
            System.out.println("Enter up to " + a.length + " nonnegative numbers.");
            System.out.println("Mark the end of the list with a negative number.");
            Scanner keyboard = new Scanner(System.in);

            double next = keyboard.nextDouble();
            int i = 0;
            for(i = 0;(next>=0 && i<a.length);i++){     //HELP!!!!
                a[i] = next;
                next = keyboard.nextDouble();
            }
            return i;
        }

推荐答案

你必须完全明白 for 循环用于了解发生了什么，以及为什么 i 10 之后循环 fillArray 。

You must understand exactly how the for loop works to understand what is going on, and why i is 10 after the for loop in fillArray.

1. 在第一个分号之前执行初始化。


2. 在第一个和第二个分号之间测试条件。如果条件是 false ，则跳出循环。


3. 执行循环体。


4. 在第二个分号（增量）后执行语句。


5. 返回步骤2.

1. Perform initialization, before the first semicolon.
2. Test the condition in between the first and second semicolons. If the condition is false, break out of the loop.
3. Execute the body of the loop.
4. Perform the statement after the second semicolon (the increment).
5. Go back to Step 2.

在 i for 循环的最后一次迭代中， i 是 9 ，并且在数组中分配了索引 9 ，步骤3.步骤4执行增量， i 现在 10 。然后然后测试条件，即 false ，并退出循环。 我现在 10 。

In the last iteration of the i for loop, i is 9, and index 9 is assigned in the array, step 3. Step 4 performs the increment, and i is now 10. Then the condition is tested, which is false, and the loop is exited. i is now 10.

但是，在你的对于循环， main ，您可以在正文中打印值，而不是之后检查循环变量。最后一次迭代是 i 是 10 ，因为条件不同： i< 11 。如果你在之后打印 i 循环，你会看到它是 11 。

However, in your main for loop, you print the value in the body instead of examining the looping variable afterwards. The last iteration is when i is 10, because the condition is different: i < 11. If you were to print i after that for loop, you'll see it's 11.

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