Add Ex 18.22

Author: jsquared21

Diff for: Exercise_18/Exercise_18_22/Exercise_18_22.class

@@ -0,0 +1,45 @@
+/*********************************************************************************
+* (Decimal to hex) Write a recursive method that converts a decimal number into  *
+* a hex number as a string. The method header is:                                *
+*                                                                                *
+* public static String dec2Hex(int value)                                        *
+*                                                                                *
+* Write a test program that prompts the user to enter a decimal number and       *
+* displays its hex equivalent.                                                   *
+*********************************************************************************/
+import java.util.Scanner;
+
+public class Exercise_18_22 {
+	/** Main method */
+	public static void main(String[] args) {
+		// Create a scanner
+		Scanner input = new Scanner(System.in);
+
+		// Prompt the user to enter a decimal number
+		System.out.print("Enter a decimal number: ");
+		int value = input.nextInt();
+
+		// Display the value's hex equivalent
+		System.out.println("The hex equivalent of "
+			+ value + " is " + dec2Hex(value)); 
+	}
+
+	/** Method converts a decimal number 
+	  * into a hex number as string */
+	public static String dec2Hex(int value) {
+		String result = "";
+		return dec2Hex(value, result);
+	}
+
+	/** Recursive helper method */
+	public static String dec2Hex(int value, String result) {
+		int r = value % 16; // Remainder
+		String remainder = r >= 10 ? 
+			String.valueOf((char)('A' + r % 10)) : String.valueOf(r);
+			
+		if (value / 16 == 0) // Base case
+			return remainder + result;
+		else
+			return dec2Hex(value / 16, remainder + result); // Recursive call
+	}
+}