0 
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

这是一个java类作业。我的这个成绩很差，因为我的教授说我使用了数字文字。我在 40 分中丢了 28 分。我设计的解决方案有这么糟糕吗？他的确切评论：

 "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."

和我的解决方案：

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);
    }
}
4

3 回答 3

3

我猜，而不是像下面这样的事情

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

他想让你使用这处length房产

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

另外，这里

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

您假设它doubles不为空，当它为空时，将引发异常

于 2013-10-23T20:54:14.877 回答
2

为了让我们能够轻松地维护这段代码，我首先要创建：

private final static int SIZE = 20;

创建双数组：

 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;            
    }         
}

显示双数组：

    /*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());
    }

我们的代码看起来更通用一些，我可以更改SIZE（如果需要）而不实际更改我的代码。

于 2013-10-23T21:02:46.140 回答
1

我同意马克西姆·舒斯汀...

只需添加一条评论

1) 不需要总是使用双精度。例如。

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

参考：原始数据类型

于 2013-10-23T21:14:28.297 回答