Thread: Conversions of Numbers in Arrays

For one of my programs, I have to convert the wind speed from knots to mph. The variable, knots, is a double. The other variable, wind, is a double [], otherwise an array. How would I convert what's in wind array from knots to mph?

Thanks.

How would I convert what's in wind array from knots to mph?

Do you have the definition of a knot? A nautical mile per hour.
A nautical mile is approximately 6000 ft.
mph is a standard mile per hour.
A standard mile is 5280 feet.
Compute the ratio and use that value to convert.

The problem I'm having is converting from an array to a double.

The problem I'm having is converting from an array to a double.

That doesn't make sense to me.
An array is a way to store and access many elements of data of the same type. You can have an array that holds any data type.
double is a data type. String is a data type. Both can be stored in an array.

Can you explain what is in the array and how you want to convert an array to a double?

The conversion problem is solved. However, I'm having a new problem. This is my code below. For some reason, I'm getting this error:

"java.lang.ArrayIndexOutOfBoundsException: 59
at Hurricanes2.main(Hurricanes2.java:56)"

and it highlights the very first "if" statement.

import java.util.Scanner;
import java.io.File;
import java.io.IOException;
public class Hurricanes2
{
    public static void main(String[] args) throws IOException
    {
        Scanner inFile = new Scanner(new File("hurcdata2.txt"));
        int numLines = 0;
 
        while(inFile.hasNextLine()) 
        { 
            inFile.nextLine(); 
            numLines++; 
        } 
        inFile.close(); 
        inFile = new Scanner(new File("hurcdata2.txt")); 
 
        int [] years = new int[numLines]; 
        String [] name = new String [numLines];
        int [] category = new int [numLines];
        int [] pressure = new int [numLines];
        double [] wind = new double [numLines];
        String [] month = new String [numLines];
 
        System.out.printf("%45s\n", "Hurricanes 1980 - 2006");
        System.out.println();
        System.out.println("Year     Hurricane     Category     Pressure (mb)     Wind Speed (mph)");
        System.out.println("=======================================================================");
 
        int i=0; 
        while(inFile.hasNext()) 
        { 
            years[i] = inFile.nextInt(); 
            month[i] = inFile.next(); 
            pressure[i] = inFile.nextInt(); 
            wind[i] = inFile.nextDouble(); 
            name[i] = inFile.next(); 
            i++; 
        } 
        inFile.close(); 
 
        for(int m = 0; m < wind.length; m++)
        {
            wind[m] = (int)((wind[m] * 1.15) * 10 + 0.5)/10.0;
        }
 
        if(wind[i]>=74 && wind[i]<=95)
        {
            category[i] = 1;
        }
        else if(wind[i]>=96 && wind[i]<=110)
        {
            category[i] = 2;
        }
        else if(wind[i]>=111 && wind[i]<=130)
        {
            category[i] = 3;
        }
        else if(wind[i]>=131 && wind[i]<=155)
        {
            category[i] = 4;
        }
        else
        {
            category[i] = 5;
        }
 
        for(int n = 0; n < years.length; n++)
        {
            System.out.printf("%1d %12s %25d %25f %25\n", years[n], name[n], category[n], pressure[n], wind[n]);
        }
 
    }
}

java.lang.ArrayIndexOutOfBoundsException: 59
at Hurricanes2.main(Hurricanes2.java:56)"

At line 56 of your program there is an array that is indexed by a value greater then the size of the array. The index was 59.

Look at line 56, find the array, and see how your code tried to use an index with the value of 59 there.