Aprioriアルゴリズムは配列の非空のサブセットjavaコードを求めます

public class Test {
        public static void main(String[] args) {
            String str="abcd" ;
            // Set 
            Set<String> set = new HashSet<String>();
            //    a     a b  c a c
            for(int i=0 ; i<str.length() ; i++){
                // 
                for(int k= i ; k<str.length() ; k++){
                    //   
                    String res = str.substring(i , k+1);
                    // 
                    if(res ==str) continue ;
                    set.add(res);
                }
            }
            // 
            for(String s : set){
                System.out.println(s);
            }
        }
}

public class Test {

    /**
     *  
     */
    public List<String> printAllSubsets(String[] array) {
        if (null == array || 0 == array.length) {
            throw new IllegalArgumentException(" Null， ");
        }
        int len = array.length;
        List<String> stringList = new LinkedList<String>();
        int allMasks = 1 << len;
        //  
        for (int i = 1; i < allMasks; i++) {
            if (i == allMasks - 1) break;
            StringBuilder s = new StringBuilder();
            for (int j = 0; j < len; j++)
                if ((i & (1 << j)) > 0) {
                    s.append(array[j]);
                }
            stringList.add(s.toString());
        }
        return stringList;
    }

    public static void main(String[] args) {
        Test exam = new Test();
        List<String> stringList = exam.printAllSubsets(new String[]{"aa", "bb", "ce", "dh"});
        for (String s : stringList) {
            System.out.println(s);
        }
    }
}