import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class Test{
 private static String[] s = new String[]{"a","b","a"};
 private static int l = s.length;
 private static List<String> list = new ArrayList<String>();
 public static void main(String[] args) {
  List<String> source = Arrays.asList(s);
  List<String> target = new ArrayList<String>();
  sort(source,target);
 }

 private static void sort(List<String> source, List<String> target) {
  if(target.size() == l){
   if(!list.contains(target.toString())){
    list.add(target.toString());
    for(int i=0;i<target.size();i++){
     System.out.print(target.get(i));
    }
    System.out.println();
   }
  }
  for(int i=0;i<source.size();i++){
   List<String> targetList = new ArrayList<String>(target);
   targetList.add(source.get(i));
   List<String> resourceList = new ArrayList<String>(source);
   resourceList.remove(i);
   sort(resourceList,targetList);
  }
 }
}

Java递归实现全排列改进(二)---利用ArrayList实现去重