Java Math

RMCircle

/**
 * Circle.java prints the area of a circle with two different radii
 * 
 * @author Rohan Mathur
 * @date 10/24/12
 * @period 7
 */

import java.util.Scanner;
public class RMCircle
{
    public static void main(String[] args)
    {
        //Initialize the variables
        Scanner keyboard = new Scanner(System.in);
        int radius; //1 + (int)(Math.random()*100); //Random Integer in the set (11,100]
        
        System.out.print("Enter an integer value radius: ");
        radius = keyboard.nextInt();
        
        if (radius <= 0)
            System.out.println("Radius is invalid. Must be greater than zero.");
        else
        {
            double area1 = Math.PI * Math.pow(radius,2);
            double circumference1 = 2 * Math.PI * radius;
            double area2, circumference2, areaRatio, circumferenceRatio;
            
            //Output the information for the first circle
            System.out.printf("The area of a circle with radius %d is %.3f\n", radius, area1);
            System.out.printf("The circumference of the circle is %.3f\n", circumference1);
            
            //Assign the values for the 
            radius *= 2;
            area2 = Math.PI * Math.pow(radius,2);
            circumference2 = 2 * Math.PI * radius;
            
            System.out.printf("The area of a circle with radius %d is %.3f\n", radius, area2);
            System.out.printf("The circumference of the circle is %.3f\n", circumference2);
            
            areaRatio = (area2 / area1);
            System.out.printf("The area ratio between the two circles is %.3f\n", areaRatio);
            
            circumferenceRatio = (circumference2 / circumference1);
            System.out.printf("The circumference ratio between the two circles is %.3f\n", circumferenceRatio);
        }
    }
}

RMPhoneNumber

/**
 * @(#)PhoneNumber.java
 *
 * Phone Number randomly a phone number using Math.random method and outputs
 * in the form (XXX) XXX-XXXX where the area code and exchange code must not begin with a 0 or 1
 * and then utilizes the printf method and DecimalFormat class to output the phone number
 *
 * @author Rohan Mathur
 * @date 10/24/12
 * @period 7
 */

import java.util.Random;
import java.text.DecimalFormat; 

public class RMPhoneNumber
{
    public static void main(String[] args)
    {
        //Utilize Math.random() to create a random area code, exchange code, 
        //  and subscriber line number (the last four digits)
        int areaCode, exchangeCode, lastFourDigits; 
        areaCode = 200 + (int) (Math.random() * 800);
        exchangeCode = 200 + (int) (Math.random() * 800);
        lastFourDigits = (int) (Math.random() * 10000);
        
        //Output using printf method in the form (XXX) XXX - XXXX
        //Hint: make sure my phone number (800) 555 - 0987 prints correctly.
        System.out.printf("(%3d) %3d - %04d\n", areaCode, exchangeCode, lastFourDigits);
        
        Random generator = new Random();
        
        areaCode = generator.nextInt(800) + 200;
        exchangeCode = generator.nextInt(800) + 200;
        lastFourDigits = generator.nextInt(10000);
        
        DecimalFormat fmt = new DecimalFormat("0000");
        
        System.out.println("(" + areaCode + ") " + exchangeCode + " - " + fmt.format(lastFourDigits));
        //System.out.printl("(%3d) %3d - %04d", areaCode, exchangeCode, lastFourDigits);
    }
}

RMQuadraticForumula

/**
 * QuadraticFormula.java
 * 
 * Computes and Solves Quadratic Equations in the form ax^2+bx+c=0
 * Outputs two solutions given to four decimal places.
 * 
 * @author Rohan Mathur
 * @date 10/24/12
 * @period 7
 */

import java.util.Scanner;
import java.text.DecimalFormat;
public class RMQuadraticFormula
{
   public static void main(String[] args)
   {
       Scanner keyboard = new Scanner(System.in);
       DecimalFormat fmt = new DecimalFormat("#.####");
       
       //Use Math.random() to assign random integers in the range [-25,25]
       int a, b, c;
       //a = (int) (Math.random() * 51) - 25;
       //b = (int) (Math.random() * 51) - 25;
       //c = (int) (Math.random() * 51) - 25;
       
       System.out.println("Solve a Quadratic Equation with integer coefficients");
       System.out.print("a = ");
       a = keyboard.nextInt();
       System.out.print("b = ");
       b = keyboard.nextInt();
       System.out.print("c = ");
       c = keyboard.nextInt();
       
       //Calculate the discriminant here
       double discriminant;
       discriminant = Math.pow(b,2) - (4 * a * c);
       //Check if discriminant is positive or negative
       if (discriminant <0 )
       {
           discriminant = Math.abs(discriminant);
           double realPart = -b / (2 * a);
           double imaginaryPart = Math.sqrt(discriminant)/(2 * a);
           
           String answer1 = realPart + " + " + imaginaryPart + "i";
           String answer2 = realPart + " - " + imaginaryPart + "i";
           System.out.printf("The solutions to %dx^2+%dx+%d=0 are %s and %s\n", a, b, c, answer1, answer2);
       }
       
       else
       {
           //Compute the two answers here
           double answer1 = ((-b + Math.sqrt(discriminant))/(2 * a));
           double answer2 = ((-b - Math.sqrt(discriminant))/(2 * a));
           
           //Output the results to four decimals in an organized format using printf
           System.out.printf("The solutions to %dx^2+%dx+%d=0 are %.4f and %.4f\n", a, b, c, answer1, answer2);
       }
   }
}