Print all permutations of a given string in Java

I want to print all permutations of a given string in Java. To do this I create one auxiliary array boolean used[] to check if I have used some character or not.

private static void permute(String s) {
        int n = s.length();
        boolean[] used = new boolean[n];
        char[] in = s.toCharArray();
        StringBuffer output = new StringBuffer();
        doPermute(in, output, used, n, 0);
    }

//helper method
private static void doPermute(char[] in, StringBuffer output,
            boolean[] used, int n, int level) {
        // TODO Auto-generated method stub
        if(n == level){
            System.out.println(output.toString());
            return;
        }
        for (int i = 0; i < in.length; i++) {
            if(used[i])
                continue;
            output.append(in[i]);
            used[i] = true;
            doPermute(in, output, used, n, level+1);
            used[i] = false;
            output.setLength(output.length()-1);
        }
    }

//main() method
public static void main(String[] args) {
        String s = "dog";
        permute(s);
    }

My main question: is there more elegant/better solution? Can I avoid using this auxiliary array (I tried to but it didn't work)?