Java: Rot13

CryptRot13.java

import java.util.*;

public class CryptRot13 {
	public static void main(String args[]) {
		Scanner scan = new Scanner(System.in);
		String value = "";
		String rotValue = "";
		
		CryptRot13 crypt = new CryptRot13();
		
		if(args.length >= 1) {
			for(int i = 0; i< args.length;i++) {
				value += args[i] + " ";
			}
		}
		else {
			System.out.print("Enter a value: ");
			value = scan.nextLine();
		}
		rotValue = crypt.convert(value);
		System.out.println("\nOld Value: " + value);
		System.out.println("New Value: " + rotValue);
		System.out.println("");
	}
	
	public String convert(String str) {
		StringBuilder val = new StringBuilder();
		for(char a:str.toCharArray()) {
			if(a >= 'A' && a <= 'Z') {
				a += 13;
				if(a > 'Z') {
					a -= 26;
				}
			}
			else if(a >= 'a' && a <= 'z') {
				a += 13;
				if(a > 'z') {
					a -= 26;
				}
			}
			val.append(a);
		}
		return val.toString();
	}
}