java 字符串 五重复 数据重组

ArrayList<String> list = new ArrayList<String>();
list.add(String.valueOf(chs.toCharArray()[chs.length()-1]));
if(chs.length() <= 1){
return list;
}
int length = chs.length();
for(int i=0; i<length-1; i++){
int count = list.size();
for(int j=0; j<count; j++){
StringBuffer sb = new StringBuffer();
sb.append(chs.toCharArray()[i]);
sb.append(list.get(j));
list.add(sb.toString());
}
list.add(String.valueOf(chs.toCharArray()[i]));
}
return list;