SquareRoot.java

package sqrt;

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

public class SquareRoot 
{
	private static NumberFormat formatter = new DecimalFormat("#0.00");   
	
	public static void main(String[] args)
	{
		/* Initialize variables and open scanner */  
		Scanner scanner = new Scanner(System.in);
		
		/* Loop until the application is closed */
		while(true)
		{
			//Get input from the user
			System.out.print("Please enter a number: ");
			String input = scanner.nextLine();
			
			try
			{
				//Parse input to a double and get the square root
				double numberInput = Double.parseDouble(input);
				double squareRoot = Math.sqrt(numberInput);

				//Format the numbers for output
				String numberInputString = parseDoubleForOutput(numberInput);
				String squareRootString = parseDoubleForOutput(squareRoot);
				
				//Output to the user
				System.out.println(String.format("The square root of %s is %s", numberInputString, squareRootString));
			}
			catch(Exception e)
			{
				//Inform the user of an error
				System.out.println("Please enter a valid number");
			}
			
			//Ask the user if they want to continue using the application and gather their input
			System.out.print("Do you want to continue using the application (Y/N)?: ");
			String finalInput = scanner.nextLine().toLowerCase();
			
			//If the input is n (or no) then exit the application and close the scanner gracefully
			if(finalInput.startsWith("n"))
			{
				System.out.println("Thanks for using the application!");
				scanner.close();
				System.exit(0);
			}
			else
			{
				//Otherwise continue
				continue;
			}
		}
	}
	
	/*
	 * This function takes a double and formats it for output taking into account large numbers which
	 * may have issues displaying normally (if the number contains E that number is simply output without formatting)
	 */
	private static String parseDoubleForOutput(double d)
	{
		if(String.valueOf(d).contains("E"))
		{
			return String.valueOf(d);
		}
		else
		{
			return formatter.format(d);
		}
	}
}