added exercise

src/main/java/com/levelup/java/exercises/beginner/GeometryCalculator.java

@@ -0,0 +1,130 @@
+package com.levelup.java.exercises.beginner;
+
+import java.util.Scanner;
+
+/**
+ * This java exercise demonstrates a solution for the geometry calculator.
+ * 
+ * @author Justin Musgrove
+ * @see <a href='http://www.leveluplunch.com/java/exercises/geometry-calculator/'>Geometry Calculator</a>
+ */
+public class GeometryCalculator {
+
+	public static class Geometry {
+		public static double areaOfCircle(double radius) {
+			return Math.PI * radius * radius;
+		}
+
+		public static double areaOfRectangle(double length, double width) {
+			return length * width;
+		}
+
+		public static double areaOfTriangle(double base, double h) {
+			return base * h * 0.5;
+		}
+	}
+
+	public static void main(String[] args) {
+
+		int choice; // The user's menu choice
+
+		do {
+			// Get the user's menu choice.
+			choice = getMenu();
+
+			if (choice == 1) {
+				calculateCircleArea();
+			} else if (choice == 2) {
+				calculateRectangleArea();
+			} else if (choice == 3) {
+				calculateTriangleArea();
+			} else if (choice == 4) {
+				System.out.println("Thanks for calculating!");
+			}
+
+		} while (choice != 4);
+	}
+
+	public static int getMenu() {
+
+		int userChoice;
+
+		// keyboard input
+		Scanner keyboard = new Scanner(System.in);
+
+		// Display the menu.
+		System.out.println("Geometry Calculator\n");
+		System.out.println("1. Calculate the Area of a Circle");
+		System.out.println("2. Calculate the Area of a Rectangle");
+		System.out.println("3. Calculate the Area of a Triangle");
+		System.out.println("4. Quit\n");
+		System.out.print("Enter your choice (1-4) : ");
+
+		// get input from user
+		userChoice = keyboard.nextInt();
+
+		// validate input
+		while (userChoice < 1 || userChoice > 4) {
+			System.out.print("Please enter a valid range: 1, 2, 3, or 4: ");
+			userChoice = keyboard.nextInt();
+		}
+
+		return userChoice;
+	}
+
+	public static void calculateCircleArea() {
+
+		double radius;
+
+		// Get input from user
+		Scanner keyboard = new Scanner(System.in);
+		System.out.print("What is the circle's radius? ");
+		radius = keyboard.nextDouble();
+
+		// Display output
+		System.out.println("The circle's area is "
+				+ Geometry.areaOfCircle(radius));
+	}
+
+	public static void calculateRectangleArea() {
+		double length;
+		double width;
+
+		// Get input from user
+		Scanner keyboard = new Scanner(System.in);
+
+		// Get length
+		System.out.print("Enter length? ");
+		length = keyboard.nextDouble();
+
+		// Get width
+		System.out.print("Enter width? ");
+		width = keyboard.nextDouble();
+
+		// Display output
+		System.out.println("The rectangle's area is "
+				+ Geometry.areaOfRectangle(length, width));
+	}
+
+	public static void calculateTriangleArea() {
+
+		double base;
+		double height;
+
+		// Get input from user
+		Scanner keyboard = new Scanner(System.in);
+
+		// Get the base
+		System.out.print("Enter length of the triangle's base? ");
+		base = keyboard.nextDouble();
+
+		// Get the height
+		System.out.print("Enter triangle's height? ");
+		height = keyboard.nextDouble();
+
+		// Display the triangle's area.
+		System.out.println("The triangle's area is "
+				+ Geometry.areaOfTriangle(base, height));
+	}
+
+}