gistfile1.txt

import java.util.List;
import java.util.LinkedList;

public class Permute {
  public static void main(String[] args) {
    for(String s : permute("abcd"))
      System.out.println(s);
  }

  public static List<String> permute(String s) {
    List<String> ret = new LinkedList<String>();
    if(s.isEmpty()) {
      ret.add("");
      return ret;
    }

    for(char c : s.toCharArray()) {
      for(String subPermute : permute(s.replaceFirst("[" + c + "]", "")))
        ret.add(c + subPermute);
    }
    return ret;
  }
}