Implementation of Lexicographic Permutation Generation. Algorithm L by Knuth. Usage: java AlgorithmL "122233344555"

AlgorithmL.java

import java.util.Arrays;

public class AlgorithmL {
    public static void main(String[] args) {
        if (args.length != 1) {
            System.err.println("Usage: provide a string (quoted if multiword)");
            System.exit(1);
        }
        char[] letters = args[0].toCharArray();
        Arrays.sort(letters);

        System.out.println(letters);
        while (true) {
            int j = letters.length - 2;
            while (letters[j] >= letters[j+1]) {
                if (j == 0) System.exit(0);
                j--;
            }
            int l = letters.length - 1;
            while (letters[j] >= letters[l]) {
                l--;
            }
            swap(letters, j, l);

            int k = j + 1;
            l = letters.length - 1;
            while (k < l) {
                swap(letters, k, l);
                k++;
                l--;
            }
            System.out.println(letters);
        }
    }

    private static void swap(char[] data, int i, int j) {
        char temp = data[i];
        data[i] = data[j];
        data[j] = temp;
    }
}