Question

Write a Java program to input a number of values into an array and then process the array by

passing it to various methods that will compute and return information we are interested in. These

include:

1. the average of the values in the array

2. the standard deviation of the values in the array

3. the number of items in the array less than the average

4. whether the array’s values are in increasing order or not

First, you need to write main. Your main method have at least four variables:

An int array

A variable for the number of items in the array

A Scanner for input

A variable of type double to store the returned average

Run your program inputting the following values:

Number of items: 5

Items: 16 25 81 80 24

Output:

Average:

45.20

Std Dev:

32.41

Less than Avg: 3

Array is not in sorted order

Run your program on the following seven sets of inputs.

1. 5 inputs: 16 25 81 80 24 (the output for this is shown above to test)

2. 10 inputs: 1000 1001 1111 1222 1775 1776 1777 1888 1997 1998

3. 1 input: 1000 (this should cause an error message that it cannot compute standard deviation)

4. 10 inputs: 1 2 3 9 8 7 4 6 12 15

5. 0 inputs (this should cause error messages that the number of inputs is out of range)

6. 20 inputs: 21 3 20 5 30 1 33 14 17 18 10 4 48 50 22 25 6 47 8 19

7. 10 inputs: 8 7 8 7 8 7 9 8 9 7

Answer 1

Source Code in Java:

import java.util.Scanner;
class ArrayStats
{
static double average(int arr[]) //function to calculate average of elements in an array
{
double total=0.0;
for(int i=0;i<arr.length;i++)
total+=arr[i]; //storing sum of elements in total
return total/arr.length; //calculating and returning average
}
static double standard_deviation(int arr[]) //function to calculate standard deviation of elements in an array
{
double average=average(arr);
double total=0.0;
for(int i=0;i<arr.length;i++)
total+=(arr[i]-average)*(arr[i]-average);
return Math.sqrt(total/(arr.length-1));
}
static int less_than_average(int arr[]) //function to check number of elements less than average in an array
{
double average=average(arr);
int count=0;
for(int i=0;i<arr.length;i++)
{
if(arr[i]<average)
count++;
}
return count;
}
static boolean is_increaing(int arr[]) //function to check if an array is in increasing order
{
for(int i=0;i<arr.length-1;i++)
{
if(arr[i]>arr[i+1])
return false;
}
return true;
}
public static void main(String args[])
{
Scanner in=new Scanner(System.in);
int n;
System.out.print("Size of array: "); //input prompt
n=in.nextInt(); //input
//validating input
if(n<=0)
{
System.out.println("Size of array is out of range. Try again with a valid size.");
return;
}
if(n==1)
{
System.out.println("Cannot compute Standard Deviation. Try again with a valid size.");
return;
}
int arr[]=new int[n]; //creating new array
System.out.println("Enter the elements one by one: "); //input prompt
for(int i=0;i<n;i++)
arr[i]=in.nextInt(); //input
//outputs
System.out.println("Average: "+average(arr));
System.out.println("Standard Deviation: "+standard_deviation(arr));
System.out.println("Count of numbers less than average: "+less_than_average(arr));
System.out.println("Array is "+(is_increaing(arr)?"":" not ")+"in sorted order");
}
}

Output: