需要帮助引用数组和数字格式

Question

I'm so lost on an assignment and need a hand! Basically, I'm suppose to write a code where users can input the number of inches of rain per month for 12 months. It will calculate the total inches, average inches, plus point out the month with the most and least rain. I have the total and average inches under control.

The most and least rain is where I'm having issues though. I know how to write the code to figure out the highest and least amount of rain fall, but I don't know how to get it to actually say which actual month in the output. It wants me to list the actual number in the array of 12 months, for instance, 7 for the seventh month.

Another issue I'm having is with the Decimal Format. I've put the import statement at the top, and I put what I thought was the right code in what I thought was the right place in the body, yet when the average is calculated, it still produces a long string of numbers. ie 12.12121314141, when I want it to display 12.1.

Any help would be greatly appreciated. Thank you in advance! Here's the code:

import java.util.Scanner;
import java.text.DecimalFormat;

public class Rainfall
{
   public static void main (String [] args)
   {
      final int MONTHS = 12;
   double[] rainFall = new double[MONTHS];

   initRain(rainFall);

   DecimalFormat formatter = new DecimalFormat("##0.0");
   System.out.println("The total rainfall for this year is " +      

            totalRain(rainFall));
   System.out.println("The average rainfall for this year is " + 
            averageRain(rainFall));
   System.out.println("The month with the highest amount of rain is " +     
            highest);
   System.out.println("The month with the lowest amount of rain is " +  

            leastRain(rainFall));
        }

   /**
  totalRain method
  @return The total rain fall in the array.
   */

   public static double totalRain(double[] rainFall)
   {
      double total = 0.0;     // Accumulator

  // Accumulate the sum of the elements in the rain fall array
  for (int index = 0; index < rainFall.length; index++)
     //total += rainFall[index];
     total = total + rainFall[index];

  // Return the total.
      return total;
   }

   /**
  averageRain method 
  @return The average rain fall in the array.
   */

   public static double averageRain(double[] rainFall)
   {
      return totalRain(rainFall) / rainFall.length;
   }

   /**
  mostRain method
  @return The most rain in the rain fall array.
   */

   public static double mostRain(double[] rainFall)
   {
  double highest = rainFall[0];

  for (int index = 0; index < rainFall.length; index++)
  {
     if (rainFall[index] > highest)
        highest = rainFall[index];
  }

  return highest;
   }

   /**
  leastRain method
  @returns The least rain in rain fall array.
   */

   public static double leastRain(double[] rainFall)
   {
  double lowest = rainFall[0];

  for (int index = 0; index < rainFall.length; index++)
  {
     if (rainFall[index] < lowest)
        lowest = rainFall[index];
  }

  return lowest;
   }

      /**
  initRain method 
  @return The rain fall array filled with user input
   */
public static void initRain(double[] array)
{
      double input;  // To hold user input.
  Scanner scan = new Scanner(System.in);

      for (int index = 0; index < array.length; index++)
  {
    System.out.print("Enter rain fall for month " + (index + 1)     

            +": ");
    array[index] = scan.nextDouble();
      }
}
}

Answer 1

For the format issue, make this:

System.out.println("The total rainfall for this year is " +      
formatter.format(totalRain(rainFall)));

And so on with all return values.

I don't get the issue regarding months thou. Could you explain it a little more?

edit. Okay, I get it. The value of index inside the loop when you assign the higuestRain,... values will be the month you are searching for ; )

Answer 2

You defined a DecimalFormat but you never use it in your program. Try

System.out.println("The average rainfall for this year is " + formatter.format(averageRain(rainFall)));

The Format classes are not global for your application you define them with your formating strings and then use format to pretty print the Number to String or parse to convert a String to Number.

Answer 3

To get the actual month you need to store the index in the array, instead of the value that index contains. In a nutshell you need to replace

highest = rainFall[index];

with

highest = index;

And that'll give you a number that goes from 0 to 11, which are the indexes available in an Array with 12 positions. If you want a number from 1 to 12, to be related to our months you can do this:

highest = index + 1

And as for the Formatter, you're never using it. Java will not use it implicitly if that's what you thought. You need to explicitly invoke it's methods to get the propper result. Something like:

formatter.format(totalRain(rainFall));

---

EDIT

To help you get the idea, here's an implementation of your mostRain method

public static double mostRain(double[] rainFall){
    double highest = rainFall[0];

    for (int index = 0; index < rainFall.length; index++)
    {
        if (rainFall[index] > rainFall[highest])
            highest = index;
    }

    return highest + 1;
}

Answer 4

For decimal format problem here is solution that you can use.

import java.text.DecimalFormat; import java.math.RoundingMode;

public class Test

{

public static void main(String args[])

{

    double i = 12.12121314141;
    DecimalFormat format = new DecimalFormat("#.#"); 
    format.setRoundingMode(RoundingMode.FLOOR);
    String s = format.format(i);
    i = Double.parseDouble(s);
    System.out.println(i); //should be 12.1

} }

Answer 5

To get the index you need 2 variables, one to store the amount of rainfall and the other to remember the index (or month):

public static double mostRain(double[] rainFall)
{
  double highest = rainFall[0];
  int monthIndex;

  for (int index = 0; index < rainFall.length; index++)
  {
    if (rainFall[index] > highest)
      highest = rainFall[index];
      monthIndex = index;
  }

  return monthIndex;
}

The method will return the index of the month with the highest rainfall, you can then use the index to retrieve the actual amount of rainfall from the array.

Answer 6

I know how to write the code to figure out the highest and least amount of rain fall, but I don't know how to get it to actually say which actual month in the output.

You can return the month rather than returning the highest rainfall in that month as follows:

public static int mostRainMonth(double[] rainFall)
{
  double highest = rainFall[0];
  int month = index;
  for (int index = 0; index < rainFall.length; index++)
  {
    if (rainFall[index] > highest)
    {
       highest = rainFall[index];
       month = index;
    }
  }

  return month;
}

You can then use this method in as follows:

int highestRainMonth = mostRainMonth(rainfall);
System.out.println("The month with the highest amount of rain is " +     
        rainfall[highestRainMonth]+" in the month "+highestRainMonth);

Another issue I'm having is with the Decimal Format. I've put the import statement at the top, and I put what I thought was the right code in what I thought was the right place in the body, yet when the average is calculated, it still produces a long string of numbers. ie 12.12121314141, when I want it to display 12.1.

You have just initialized the DecimalFormatter object, but you haven't used it anywhere. You can use the setMaximumFractionDigits method as follows:

DecimalFormat df = new DecimalFormat("##0.0");
System.out.println("The average rainfall for this year is " + 
        formatter.format(averageRain(rainFall)));