gistfile1.txt

public class Ensayo {
	public static void main(String[] args) {
		String inv = "";
		System.out.println(convertir("1234", inv));
	}
	public static String convertir(String num,String inv) {
		for (int i = num.length() - 1; i >= 0; i--) {
			inv += num.charAt(i);
		}return inv;
	}
}