import java.util.Scanner;
public class Calculator {

	
	public double result = 0.0;
	public double input = 0;
	public String operator;
	
	
	public Calculator(double result, double input, String operator) {
		
		this.result = result;
		this.input = input;
		this.operator = operator;
	}

	public double add(double result, double input)
	{
		return result + input;
	}

	public double subtract(double result, double input)
	{
		return result - input;
	}

	public double divide(double result, double input)
	{
		return result/input;
		
	}

	public double multiply(double result, double input)
	{
		return result * input;
	}

	public void doCalculations()
	{
	Calculator calc = new Calculator(0, 0, "None yet");
	boolean done = false;
	Scanner keyboard = new Scanner(System.in);
	System.out.println("Calculator is on.  " +
			"Enter a space between the operator and the second number.");
	while (done == false)
	{
		System.out.println("Result is " + result);
		operator = keyboard.next();
		input = keyboard.nextDouble();
		try {
		if (operator.equals("+"))
		{
			result = calc.add(result, input);
			System.out.println("Result + " + input + " = " + result);
			System.out.println("New result = " + result);
		}
		
		else if(operator.equals("-"))
		{
			result = calc.subtract(result, input);
			System.out.println("Result - " + input + " = " + result);
			System.out.println("New result = " + result);
		}
		else if(operator.equals("/"))
		{
			result = calc.divide(result, input);
			System.out.println("Result / " + input + " = " + result);
			System.out.println("New result = " + result);
		}
		else if(operator.equals("*"))
		{
			result = calc.multiply(result, input);
			System.out.println("Result * " + input + " = " + result);
			System.out.println("New result = " + result);
		}
		else if(operator.equalsIgnoreCase("r"))
		{
			System.out.println("Final result = " + result);
			System.exit(0);
		}
		else throw new UnknownOperatorException(operator);
		}
		catch(UnknownOperatorException e)
		{
			System.out.println(operator + " is not a valid operator." );  
			calc.doAgain(result);
		}}
		
	}
		
public void doAgain(double result)
{
	Scanner keyboard = new Scanner(System.in);
	System.out.println("Please re-enter your last line of input.  " +
	"Remember the space between operator and number.");
	operator = keyboard.next();
	input = keyboard.nextDouble();
	
	
}

	

}