遞歸算法實現全排列

public class FullSort {  
    //將NUM設置爲待排列數組的長度即實現全排列  
    private static int NUM = 3;  
  
    /** 
     * 遞歸算法：將數據分爲兩部分，遞歸將數據從左側移右側實現全排列 
     * 
     * @param datas 
     * @param target 
     */  
    private static void sort(List datas, List target) {  
        if (target.size() == NUM) {  
            for (Object obj : target)  
                System.out.print(obj);  
            System.out.println();  
            return;  
        }  
        for (int i = 0; i < datas.size(); i++) {  
            List newDatas = new ArrayList(datas);  
            List newTarget = new ArrayList(target);  
            newTarget.add(newDatas.get(i));  
            newDatas.remove(i);  
            sort(newDatas, newTarget);  
        }  
    }  
  
    public static void main(String[] args) {  
        String[] datas = new String[] { "a", "b", "c", "d" };  
        sort(Arrays.asList(datas), new ArrayList());  
    }  
  
}