/*
 * This program demonstrates arrays.
 * Arrays are an indexed collection of variables that use the same name, are of the same type and are in continuous memory locations.
 * In this program, we will demonstrate arrays of primitive types, declraring and initializing arrays and passing arrays as 
 * parameters to methods.
 */
import java.util.Scanner;
class ArrayExample
{
	public static void main (String [] args)
	{
		Scanner input = new Scanner (System.in);

		//Arrays are set up in two steps. We need to declare them first and then create the array.
		//Here, we create an array of 10 doubles.
		// Step 1: declaration. This just creates a reference to the array. The array doesn't exist yet.
		double [] myArray;

		//Step 2: Actually create the array. Memory allocation happens here.
		myArray = new double[10];

		// The 2 steps can be combined into double [] myArray = new double[10];

		//Reading in 10 doubles from the user.
		System.out.println("Please enter 10 floating point variables.");
		
		//Arrays and for loops work very well together. We are going to use a for loop to read in 10 values.

		for(int i=0; i<myArray.length;i++)
		{
			//The array.length property contains the length of the array (10, in this case).
			//The array has elements indexed from 0 through 9. Each element is reached using the [] operator.
			double num = input.nextDouble();
			myArray[i]=num;
		}

		//We then call the sumElements method we have written below to print the sum of the elements.
		System.out.println("The sum of the elements is "+sumElements(myArray));
		//When we pass an array as a paramater, we don't need the [] operator.
	}

	/* This method adds up the values in the array passed in as a parameter.
	 * We need the [] operator in the parameter list.
	 * Arrays are passed by reference. Any changes made to the array in the method will be preserved across the method call.
  	 */
	static double sumElements ( double [] arr)
	{
		double sum=0;
		for(int i=0; i<arr.length;i++)
			sum = sum + arr[i];
		return sum;
	}
}