java數組分配-使用數字文字

Question

Create an application containing an array that stores 20 double values, 
such as 2.34, 7.89, 1.34, and so on. The application should:
     *      Display the sum of all the array elements
     *      Display the average of all the array elements
     *      Display the largest value of all the array elements

這是一個Java類分配。 我對這門課程的評分很差，因為我的教授說我使用了數字文字。 我在40分中失去了28分。我設計的解決方案太差了嗎？ 他的確切評論：

 "The program you submitted uses numeric literals in place of the array’s length. 
 This cause several runtime errors when I change the size of your array and tested the code."

和我的解決方案：

import java.util.Random; 
import java.util.Arrays;

public class MyArray{ 
  public static double[] doubles;

    public static void main(String args[]) {
       MyArray.createDoublesArray();
       MyArray.displayDoublesArray();
       MyArray.displaySum();
       MyArray.displayAverage();
       MyArray.displayTheLargestValue();
    } 

    /*Fill up the double Array class member*/
    public static void createDoublesArray(){
        doubles = new double[20];
        //Create Random object 
        Random r=new Random(); 
        double rangeMin = 1, rangeMax = 9; 
        //Generate random double number - 20 times within the range of 2 to 9
        for(int i=0;i<20;i++) { 
            //Generate random double numbers and round them to the two decimal places
            double randomdouble = Math.round((rangeMin + (rangeMax - rangeMin) * r.nextDouble())*100.0)/100.0; 
            doubles[i] = randomdouble;            
        }         
    }    

    /*Display the double Array*/
    public static void displayDoublesArray(){
        String delimiter;
        Arrays.sort(doubles);
        System.out.println("The double array: ");
        // iterate through all the array elements
        System.out.print("{");
        for(int i=0;i<20;i++) { 
           if(i < 19){
               delimiter = ", ";
           }
           else{
               delimiter = "}";
           }
           System.out.print(doubles[i]+ delimiter);      
        } 
        System.out.println("\n");
    }

    /*Displays the sum of the double array.*/
    public static void displaySum() {
        //initialize the sum with 0
        double sum = 0.0;

        // iterate through all the array elements
        for (int i = 0; i < doubles.length; i++) {
            // add up each element to the sum variable
            sum += doubles[i];
        }

        // display the sum
        System.out.println("The sum is: " + Math.round(sum*100.0)/100.0 + "\n");
    }

    /*Displays the average of the double array.*/
    public static void displayAverage() {
        // initialize the sum with 0
        double sum = 0.0;

        // iterate through all the array elements
        for (int i = 0; i < doubles.length; i++) {
            sum += doubles[i];
        }
        // display the average by dividing the sum to the length of the array
        System.out.println("The average is: " + Math.round((sum / doubles.length)*100.0)/100.0 + "\n");
    }

    /*Displays the largest value from the double array */
    public static void displayTheLargestValue() {
        //initialize the largest value with the first element
        double largestValue = doubles[0];

        //iterate through the remaining elements (ignore the first)
        for (int i = 1; i < doubles.length; i++) {
            // check if "i" element is greater then the current largest value
            if (doubles[i] > largestValue) {
                largestValue = doubles[i];
            }
        }
        // display the largest value
        System.out.println("The largest value is: " + largestValue);
    }
}  

Answer 1

我猜想不是這樣的事情

  for(int i=0;i<20;i++)

他希望您使用length屬性

  for(int i=0;i<doubles.length;i++)

另外，這里

    //initialize the largest value with the first element
    double largestValue = doubles[0];

您假設doubles不為空，當doubles為空時，將引發異常

Answer 2

為了讓我們輕松維護此代碼，我將首先創建：

private final static int SIZE = 20;

createDoublesArray ：

 public static void createDoublesArray(){
    doubles = new double[SIZE];
    //Create Random object 
    Random r=new Random(); 
    double rangeMin = 1, rangeMax = 9; 
    //Generate random double number - 20 times within the range of 2 to 9

    double randomdouble = 0.0;  // <- we don't want to initiate double in 'for' loop

    for(int i=0;i<SIZE;i++) { 
        //Generate random double numbers and round them to the two decimal places
        randomdouble = Math.round((rangeMin + (rangeMax - rangeMin) * r.nextDouble())*100.0)/100.0; 
        doubles[i] = randomdouble;            
    }         
}      

displayDoublesArray：

    /*Display the double Array*/
       public static void displayDoublesArray(){
        String delimiter;
        Arrays.sort(doubles);
        System.out.println("The double array: ");
        // iterate through all the array elements

        StringBuilder buff = new StringBuilder(); // use buffer 

        buff.append("{");
        for(int i=0;i<SIZE;i++) { 
           if(i < SIZE-1){
               delimiter = ", ";
           }
           else{
               delimiter = "}";
           }
           buff.append(doubles[i]+ delimiter);                  
        } 

        buff.append("\n");

        System.out.println(buff.toString());
    }

我們的代碼似乎更通用，我可以更改SIZE （如果需要），而無需實際更改我的代碼。

Answer 3

我同意Maxim Shoustin ...

只需添加一條評論

1）不必總是使用double。 例如

double rangeMin = 1, rangeMax = 9; //can be replaced by int. 

ref：基本數據類型