Add Ex 18.2

Author: jsquared21

Exercise_18/Exercise_18_02/Exercise_18_02.class

@@ -0,0 +1,58 @@
+/*********************************************************************************
+* (Fibonacci numbers) Rewrite the fib method in Listing 18.2 using iterations.   *
+* Hint: To compute fib(n) without recursion, you need to obtain fib(n - 2) and   *
+* fib(n - 1) first. Let f0 and f1 denote the two previous Fibonacci numbers. The *
+* current Fibonacci number would then be f0 + f1. The algorithm  can be          *
+* described as follows:                                                          *
+*                                                                                *
+* f0 = 0; // For fib(0)                                                          *
+* f1 = 1; // For fib(1)                                                          *
+*                                                                                *
+* for (int i = 1; i <= n; i++) {                                                 *
+* 		currentFib = f0 + f1;                                                      *
+* 		f0 = f1;                                                                   *
+* 		f1 = currentFib;                                                           *
+* }                                                                              *
+* // After the loop, currentFib is fib(n)                                        *
+*                                                                                *
+* Write a test program that prompts the user to enter an index and displays its  *
+* Fibonacci number.                                                              *
+*********************************************************************************/
+import java.util.Scanner;
+
+public class Exercise_18_02 {
+	/** Main method */
+	public static void main(String[] args) {
+		// Create a Scanner
+		Scanner input = new Scanner(System.in);
+
+		// Prompt the user to enter an index
+		System.out.print("Enter an index for a Fibonacci number: ");
+		int index = input.nextInt();
+
+		// Find and display the Fibonacci number
+		System.out.println("The Fibonacci number at index " 
+			+ index + " is " + fib(index));
+
+	}
+
+	/** The method for finding the Fibonacci number */
+	public static long fib(long index) {
+		long f0 = 0; // For fib(0)         
+		long f1 = 1; // For fib(1)
+		long currentFib = 0;  
+
+		if (index == 0)
+			return f0;
+		else if (index == 1)
+			return f1;       
+      else {
+			for (int i = 1; i < index; i++) {
+				currentFib = f0 + f1;     
+				f0 = f1;                  
+				f1 = currentFib;          
+			} 
+			return currentFib;                            
+      }                       
+	}
+}